Inaugurated in 1994 in Como, Italy, this series of conferences has become an important forum for scientists working on strong interactions, stimulating exchanges among theorists and experimentalists as well as across related fields.
The twelfth edition of this conference series will take place in Thessaloniki (Greece) from 29th August to 3rd September 2016 in Makedonia Palace conference centre. Thessaloniki, founded more than 2500 years ago in the north Greece, overlooking the gulf of Thermaikos, has always been a meeting point for people of different cultures. Today, a modern city with marks of the past, is an inspiring place welcoming international events and conferences.
This edition of the conference is dedicated to the memory of Michael MüllerPreußker. His scientific contribution will be remembered during the conference.
The conference will also include a variety of events addressing school children and general public as well as different cultural events open to the public.
The conference will be followed by a Workshop on "Accelerators Revealing the QCD Secrets" that will take place from 3rd to 5th September 2016 in Makedonia Palace conference centre.
The Student Lectures are scheduled to take place on Sunday, August, 28, from 13:00 until 20:15.
PhD students, young postdocs and all other interested people are encouraged to join.
QCD with chiral(axial) chemical potential will be reconstructed with the help of effective low energy Lagrangians and different models of NJL type. Their thermodynamic properties will be confronted to lattice predictions. Possible signatures of chiral imbalance will be guessed.
We will present new methods to compute the parton distributions, the proton charge radius and the neutron electric dipole moment. We will demonstrate the applicability of our methods using twisted mass fermion configurations and compare to the results of other lattice QCD collaborations. Finally we will discuss future directions and perspectives for baryon structure studies within lattice QCD.
The overarching science challenges for the coming decade are to discover the meaning of confinement, its relationship to dynamical chiral symmetry breaking (DCSB)  the origin of visible mass  and the connection between these two, key emergent phenomena. There is strong evidence to suggest that they are intimately connected with the appearance of momentumdependent masses for gluons and quarks in QCD, which are large in the infrared: $m_g \sim 500\,$MeV and $M_q \sim 350\,$MeV. DCSB, expressed in the dynamical generation of a dressedquark mass, has an enormous variety of verifiable consequences, including an enigmatic result that the properties of the (almost) massless pion are the cleanest expression of the mechanism which is responsible for almost all the visible mass in the Universe. These emergent phenomena are expressed with particular force in the partonic structure of hadrons, e.g. in valencequark parton distribution amplitudes and functions, and, consequently, in numerous hadronic observables, including elastic and transition form factors. This presentation will highlight that with the identification of these connections we are now in a position to exhibit the consequences of confinement and DCSB in a wide range of hadron observables, opening the way to empirical verification of their expression in the Standard Model.
The HEP Inquiry learning resources created over the last threefour years by the Inspiring Science Education and Golab European outreach projects will be reviewed. The resources are mostly addressed to high school students and the purpose is to ignite their interest on science. To that end, science exhibitions as well as science fairs (like the ones organized by this conference) try to reach a very wide audience.
In addition, at the University of Athens for the last four years we have been using the HYPATIA online event analysis tool as a lab course for fourth year undergraduate physics students, majoring in HEP. Each year 2530 students highly appreciated the course, since they get a direct involvement in the actual toplevel research. Up to now, the course was limited to visual inspection of a few tenths of ATLAS events. Recently we have enriched the course with additional analysis exercises, which involve large samples of events. The students, through a user friendly interface can analyze the samples (both signal and background ones) and optimize the cut selection in order to search for the Higgs decay H>4 leptons. Recently ATLAS released 1/fb of data, so starting next fall the students will analyse real data
We present a status report of our current knowledge of parton distribution functions in the nucleon, including the flavor and spin decomposition, using the latest information from experiments ranging from lowerenergy fixed target facilities to the highestenergy hadron colliders.
Section A: Vacuum Structure and Confinement
Mechanisms of quark confinement (vortices, monopoles, calorons...) and the structure of the vacuum in nonAbelian gauge theories. Chiral symmetry breaking, and the Dirac spectrum in the lowmomentum region. Studies of ghost and gluon propagators. Confining strings and flux tubes, their effective actions. Renormalons and power corrections. Interface between perturbative and nonperturbative physics.
Conveners: D. Antonov (Heidelberg), M. Faber (TU Vienna), J. Greensite (San Francisco State U)
Focus Subsection: Emergent gauge fields and chiral fermions
Chiral Fermions and anomalous hydrodynamic effects in condensed matter systems, quantum simulators of QCD, topological phenomena in condensed matter systems.
Conveners: T. Schaefer (NC State U), V. Shevchenko (NRC Kurchatov I.)
X
I will review recent results obtained within the Hamiltonian approach to QCD in Coulomb gauge at finite temperatures. The temperature is introduced by compactifying a spatial dimension. Results are presented for the chiral and dual quark condensate as well as for the Polyakov loop and the pressure
We discuss the phenomenon of (inverse) magnetic catalysis for both the deconfinement and chiral transition. We discriminate between the hard and soft wall model, which we suitably generalize to include a magnetic field. Our findings show a critical deconfinement temperature going down, in contrast with the chiral restoration temperature growing with increasing magnetic field. This is at odds with contemporary lattice data, so the quest for a holographic QCD model capable of capturing inverse magnetic catalysis in the chiral sector remains open.
We outline further directions in this research.
This talk is based on joint work with Diego Rocha Granado and Thomas Mertens (see http://inspirehep.net/record/1404170?ln=en).
Essential nonperturbative dynamical features of QCD are well captured in a semiclassical effective theory based on the extension of superconformal quantum mechanics to the lightfront and its holographic embedding in a higher dimensional gravity theory. This new approach to hadron physics incorporates confinement, the appearance of a massless pion, and Regge spectroscopy consistent with experiment. It also gives remarkable connections between the meson and baryon spectrum. In this talk I will discuss the extension of this approach to describe the structure of heavylight bound states and the perturbativenonperturbative interface in QCD.
Section B: Light Quarks
Chiral and soft collinear effective theories; sum rules; lattice; SchwingerDyson equations; masses of light quarks; lightquark loops; phenomenology of lighthadron form factors, spectra and decays; structure functions and generalized parton distributions; exotics and glueballs; experiments.
Conveners: J. Goity (Hampton U.), B. Ketzer (Bonn U.), H. Sazdjian (IPN Orsay), N. G. Stefanis (Ruhr U. Bochum), H. Wittig (JGU Mainz)
We discuss the use of lightfront field theory in the descriptions of hadrons.
In particular, we clarify the confusion in the prevailing notion of the equivalence between the infinite momentum frame and the lightfront dynamics and the advantage of
the lightfront dynamics in hadron physics. As an application, we present our recent work on the flavor asymmetry in the proton sea and identify the presence of the deltafunction contributions associated with endpoint singularities arising from the chiral effective theory calculation. The results pave the way for phenomenological applications of pion cloud models that are manifestly consistent with the chiral symmetry properties of QCD.
I will review recent lattice results on the meson and baryon spectrum with a focus on the determination of hadronic resonance masses and widths using a combined basis of singlehadron and hadronhadron interpolating fields. I will emphasize how these mostly exploratory calculations differ from traditional lattice QCD spectrum calculations for states stable under QCD.
A wealth of information on the properties of hadrons of both
theoretical and experimental interest can be provided by lattice
methods. This includes wavefunctions, their response to electromagnetic, weak
or beyond the Standard Model probes and their internal dynamics in
terms of the contributions from quarks and gluons. Tremendous progress
has been achieved recently in the evaluation of benchmark quantities
which are well determined from experiment as well as more challenging
and less well known observables. I present selected highlights of
recent calculations, including the nucleon charges and form factors,
nucleon sigma terms and the distribution amplitudes of baryons and
mesons.
We will discuss the extraction of the axial, scalar and tensor charges using twisted mass fermions with simulations at a physical value of the u and quark mass. In addition, we will discuss the nucleon sigmaterms and compare the results obtained recently within lattice QCD.
Section C: Heavy Quarks
Heavylight mesons, heavy quarkonia, heavy baryons, heavy exotics and related topics: phenomenology of spectra, decays, and production; effective theories for heavy quarks (HQET, NRQCD, pNRQCD, vNRQCD, SCET); sum rules for heavy hadrons; lattice calculations of heavy hadrons; heavyquark masses determination; experiments.
Conveners: G. Bodwin (Argonne NL), P. Pakhlov (ITEP, Moscow), J. Soto (U. Barcelona), A. Vairo (TU Munich)
Heavy quarks (charm and beauty) are interesting probes to study the QuarkGluon Plasma (QGP) in highenergy heavyion collisions, since they are produced in initial hard partonic scattering processes on a short time scale and experience the whole evolution of the medium. They are expected to traverse the QCD medium, interacting with its constituents and losing energy through radiative and collisional processes. As a consequence of these interactions, the momentum distributions of open heavyflavour hadrons are modified. A strong modification of the transversemomentum distributions of heavyflavour hadrons in PbPb collisions with respect to binaryscaled pp collisions is observed, via the measurement of the nuclear modification factor RAA. The azimuthal distribution of heavyflavour hadrons, in particular the elliptic flow ν2, reflects the initial spatial anisotropy of the overlap of the colliding nuclei. The elliptic flow brings information on the medium transport properties: on the question whether heavy quarks take part in the collective expansion of the medium at low pT, and on the pathlength dependence of parton energy loss at high pT. Heavyflavour measurements in pp collisions not only provide the necessary baseline to understand the results in PbPb collisions. They are also an important test of perturbative QCD calculations. Moreover, heavyflavour production in pPb collisions is affected by cold nuclear matter effects in the initial and final state, such as modification of parton densities in nuclei, kT broadening and gluon radiation. Heavyflavour measurements in pPb collisions can help to disentangle the influence on particle production of those effects from that of the QGP formation.
In ALICE, opencharm production is studied through the reconstruction of the hadronic decays of D0, D+, D*+ and Ds+ mesons at midrapidity. The high precision tracking, good vertexing capabilities and excellent particle identification offered by ALICE allow for the measurement of particles containing heavy quarks (particularly D mesons) in a wide transversemomentum range in pp, pPb and PbPb collisions.
In this talk, a review of the main results on Dmeson production in pp collisions at √𝑠 = 7 TeV, pPb collisions at √𝑠NN = 5.02 TeV and PbPb collisions at √sNN = 2.76 TeV will be presented.
We present results of simulations of the RQCD Collaboration on open charm states, including a scattering analysis of scalar and axialvector $D_s$ mesons near the physical pion mass, utilizing different spatial volumes. The spectra are obtained, using $N_f=2$ QCDSF and RQCD as well as $N_f=2+1$ CLS ensembles, employing nonperturbatively improved Wilson fermions. In the latter case, extrapolations to the physical point are performed along two lines in the quark mass plane: keeping the strange quark mass constant and keeping the sum of the three sea quark masses (approximately) constant.
The extraction of the $B \to K^*$ transition form factors from lattice data at (close to) physical pion masses is discussed. The possible mixing of $\pi K$ and $\eta K$ states is taken into account. Applying nonrelativistic effective field theory in a finite volume, the twochannel analogue of the LellouchLuscher formula is reproduced. Due to the resonance nature of the $K^*$ , it is shown how the form factors can be determined at the pole position in a processindependent manner. The infinitelynarrow width approximation of the results is also discussed.
We analyze longdistance QCD effects in $B_{d,s}\to\ell^+\ell^\gamma$ decays.
Taking into account photon emission from the $b$quark loop, weak annihilation,
and Bremsstrahlung from leptons in the final state, we give predictions
for dilepton spectrum and various asymmetries in $B_{d, s}\to \ell^+\ell^\gamma$ decays within the Standard Model.
We present the results of our recent calculations of the hadronic form factors for semileptonic decays of B mesons and the matrix elements of local operators contributing to neutral B and Bs meson mixing. From joint fits of the lattice results and the experimental data we are able to determine the magnitude of the CKM matrix elements Vub and Vcb, and also (with Vtb as an additional input) the matrix elements Vtd and Vts. These calculations were performed on 2+1 flavor MILC asqtad configurations with the Fermilab Wilson clover action for the charm and bottom quarks. The variety of lattice spacings and sea and valence quark masses allows for controlled continuum and chiral extrapolations.
We present a lattice QCD study of coupledchannel $D\pi$, $D\eta$ and $D_{s}\bar{K}$
scattering, as well singlechannel $DK$ scattering. Our methodology allows us to determine precise finite volume spectra which we use to constrain scattering amplitudes as a function of energy. We interpret our results in terms of poles in the $S$matrix and provide a measure of the coupling of each channel to a given pole. By exploring $S$, $P$ and $D$ wave interactions we comment on the nature of states with $J^{P} = 0^{+}$, relevant for the $D^{*}_{0}(2400)$ and $D^{*}_{s0}(2317)$, as well as states with $J^{P} = 1^{}, 2^{+}$.
Section D: Deconfinement
QCD at finite temperature; quarkgluon plasma detection and characteristics; jet quenching; transportation coefficients; lattice QCD and phases of quark matter; QCD vacuum and strong fields; heavyion experiments.
Conveners: C. Allton (Swansea U.), E. Iancu (CEA/DSM/Saclay), M. Janik (WUT), P. Petreczky (BNL), A. Vuorinen (U. Helsinki), Y. Foka (GSI)
Kinetic theory is one of the main dynamical frameworks to model ultrarelativistic heavyion collisions at RHIC and the LHC. For example, it has been used to study i) thermalization during the early partonic stage of the collision, ii) hadronic mixture evolution in late stages of the reaction, and more recently also iii) proper inclusion of nonthermal phase space density corrections for particles coming from a dissipative quarkgluon fluid. It is wellknown that at large enough opacities onshell kinetic theory gives back hydrodynamics (this has been used, for example, to systematically formulate causal versions of relativistic dissipative hydrodynamics). The practical question is how high opacities need to be for hydrodynamic behavior in the rapidly expanding small systems present in heavy ion reactions. I will address this in light of recent results from the AMPT transport model that can explain, with unexpectedly modest opacities, features in the data that have traditionally been thought to be the hallmarks of hydrodynamics.
This talk will review recent progress in using holography to learn lessons about heavy ion collisions. I will illustrate the use of holography for the earliest stage of HIC, before hydrodynamics applies, and also during the hydrodynamic evolution in order to describe the energy loss and shape evolution of jets traversing the hydrodynamic medium. Interesting results include the fast applicability of hydrodynamics (within 0.1 fm/c), a Gaussian rapidity profile of the energy density, and a characteristic dependence of energy loss on the width of a jet.
N/A
We numerically solve 2+1D effective kinetic theory of weak coupling QCD under longitudinal
expansion relevant for early stages of heavyion collisions. We find agreement with viscous hydrodynamics and classical YangMills simulations in the regimes where they are applicable. With a reasonable initial condition for the anisotropic system in the heavy ion collisions, we found that the system is approximately described by viscous hydrodynamics well before τ ~ 1.0 fm/c.
Section E: QCD and New Physics
Physics beyond the Standard Model with hadronic physics precision experimental data and precision calculations.
Conveners: W. Detmold (MIT), M. Gersabeck (U. Manchester), F. J. LlanesEstrada (UC Madrid), E. Mereghetti (Los Alamos NL), J. Portoles (IFIC, Valencia)
Rare electroweak penguin processes provide a rich platform to search for new physics. Some deviations have recently been found between the rate and angular distribution of these processes measured by the LHCb experiment and theoretical predictions. In addition, LHCb has seen hints of lepton universality breaking in these rare processes. This talk will review these measurements and put them in the context of search for new physics.
I review the theory of the search for new physics with rare flavourchanging processes, some of which may indicate departures from the Standard Model, with an emphasis on the StandardModel predictions and their uncertainties. I will focus on semileptonic B decays, but will also discuss recent developments and prospects in K physics.
The LHC has found several anomalies in exclusive semileptonic b > s mu mu decays with a global significance of more than 4 sigma. I will discuss the hadronic uncertainties entering the theoretical prediction for the relevant decays and present modelindependent global fits of new physics to the data. The discrimination between highscale new physics and lowenergy QCD effects, as well as the possibility of leptonflavour universality violation are discussed.
Lattice QCD calculations with dynamical fermions are getting more and more precise in recent years. The uncertainties of lattice QCD results can be shrinked systematically. I will discuss lattice QCD calculations of weak matrix elements related to quark flavor anomalies in bottom quark decays.
In this talk, the latest results of searches for the standard model Higgs boson produced in association with a top quarkantiquark pair (ttH), where Higgs decays into photons, bottom quarkantiquark pair or leptons via WW, ZZ and tautau will be presented. The analyses have been performed using the 13 TeV pp collisions data recorded by the CMS experiment in 2015. The results are presented in the form of the best fit to the signal strength (mu=sigma/sigmaSM) measured with respect to the Standard Model prediction and its expected and observed 95% CL upper limits.
The top quark is the heaviest known fundamental particle. As it is the only quark that decays before it hadronizes, this gives us the unique opportunity to probe the properties of bare quarks and to test perturbative QCD. This talk will focus on a few recent precision top quark measurements by the ATLAS Collaboration: fiducial top pair and single top production cross sections including differential distributions will be presented and compared with QCD predictions. The results include the first top quark measurements at 13 TeV using data from LHC run 2.
Section F: Nuclear and Astroparticle Physics
Nuclear matter; nuclear forces; quark matter; neutron and compact stars.
Conveners: M. Alford (Washington U. in St.Louis), D. Blaschke (U. Wroclaw), T. Cohen (U. Maryland), L. Fabbietti (TU Munich), A. Schmitt (U Southampton)
Chirality of neutrinos modifies the conventional hydrodynamic behavior at the macroscopic scale and leads to anomalous transport phenomena in neutrino matter. We argue that such chiral transport of neutrinos should play important roles in the evolution of corecollapse supernovae, and, in particular, leads to the possible inverse energy cascade from small to large scales, which may be relevant to the origin of the supernova explosion.
Dense matter in the core of neutron stars is strongly coupled and presents an enormous theoretical challenge. Firstprinciple methods from QCD are currently known only for vanishing or asymptotically large densities, while phenomenological models are usually restricted to either nuclear or quark matter and/or contain many unknown parameters. I will discuss whether and how holographic methods can help. In particular, I will present latest work on nuclear matter and the chiral phase transition to quark matter in the SakaiSugimoto model, potentially leading to a strongly coupled equation of state with only 3 parameters that is applicable over a wide density regime.
I will discuss recent advances in the perturbative description of the thermodynamic properties of cold unpaired quark matter. After presenting new results for the temperature dependence of the Equation of State (EoS), I will describe recent advances in determining the next fourloop term in the weak coupling expansion of the zerotemperature EoS. The potential implications of these results to neutron star phenomenology will be discussed in detail.
We propose an astrophysical scenario in which hadronic stars and quark stars coexist. While hadronic stars would populate a branch of very compact objects (radii measurements indicate the existence of such configurations in some cases), quark stars would instead populate a branch of very massive stars (e.g. the two solar mass star PSR J16142230). The conversion process between a hadronic star and a quark star will be discussed in its turbulent and diffusive regimes and its phenomenological consequences for long and short gammaraybursts will be also presented in connection with the protomagnetar model.
Based on:
Phys.Rev. D89 (2014) no.4, 043014
Phys.Rev. C92 (2015) no.4, 045801
Eur.Phys.J. A52 (2016) no.2, 40
Eur.Phys.J. A52 (2016) no.2, 41
Phys.Rev. D93 (2016) no.10, 103001
Section G: Strongly Coupled Theories
Hints on the confinement/deconfinement mechanisms from supersymmetric and string theories; strongly coupled theories beyond the Standard Model; applications of nonperturbative methods of QCD to other fields.
Conveners: D. Espriu (U. Barcelona), Z. Fodor (BU Wuppertal), E. Kiritsis (APC and U. Crete), F. Sannino (CP3Origins), A. Weiler (TU Munich)
Talk based on paper by
G. Triantaphyllou, EJTP 13, No. 35 (2016) 115–144
http://www.ejtp.com/articles/ejtpv13i35p115.pdf
We present the inelastic scattering between $\gamma\gamma$ into/out of a strongly interacting EWSBS satisfying unitarity. The matrix elements $V_L V_L\to V_L V_L $, $V_L V_L \to hh$, $hh\to hh$, $V_L V_L \to \gamma \gamma$ and $hh \to \gamma \gamma$ are al computed to NLO in perturbation theory with the Nonlinear Effective Theory of the EWSBS (within the Equivalence Theorem).
Describing the EWSBS itself requires seven parameters: two LO parameters ($a$, $b$) and the NLO counterterms ($a_4$, $a_5$, $g$, $d$, $e$). The coupling with the $\gamma\gamma$ state requires four additional ones:
$c_{\gamma\gamma}$ and $a1$, $a2$, $a3$, though in the combination $a_1a_2+a_3$ only, so the number of total coefficients is 9.
By means of a modified version of the IAM and N/D unitarization procedures, we study the prospects for detecting any new strongEWSBS resonances in the energy range 0.753TeV, within reach of the LHC. Our basic assumption is that the couplings with $\gamma\gamma$ are feeble as they are governed by the electromagnetic $\alpha_{\rm ew}$, while the EWSBS is strongly interacting.
There are two cases of interest. First, the detection of resonances in the diphoton channel coming from the strong rescattering of $V_L V_L$ states (photons in the final state). And second, the possible study of $\gamma\gamma$ scattering at the LHC by means of the new forward detectors (CMSTOTEM and ATLASAFP) that tag the elastically scattered proton (photons in the initial state). Of course, this would be also a goal for the ILC and its future detectors.
By means of forward sumrules for γγ and gg scattering we show that a spin0 resonance with mass of the order of the TeV and a sizable γγ or gg partial width of the order of a few GeV must be accompanied by higher spin resonances with JR≥2 with similar properties, as expected in strongly coupled extensions of the Standard Model or, alternatively, in higher dimensional deconstructed duals. Furthermore, independently of whether the 750 GeV diphoton candidate is a scalar or a tensor, the large contribution to the forward sumrules in the referred scenario implies the presence of states in the spectrum with JR≥2, being these high spin particles a manifestation of new extradimensions or composite states of a new strong sector.
The fermonic Green’s functions of QCD exhibit an unexpected property of `effective locality’, which is exact. In the strong coupling limit, at quenching and eikonal approximations, effective locality implies a dependence of nonperturbative fermonic Green’s functions on both $C_{2f}$ and $C_{3f}$ Casimir operators, that is, on the full algebraic content of the $SU(3)$ rank2 color algebra. This result seems to extend beyond the approximations being used.
Section A: Vacuum Structure and Confinement
Mechanisms of quark confinement (vortices, monopoles, calorons...) and the structure of the vacuum in nonAbelian gauge theories. Chiral symmetry breaking, and the Dirac spectrum in the lowmomentum region. Studies of ghost and gluon propagators. Confining strings and flux tubes, their effective actions. Renormalons and power corrections. Interface between perturbative and nonperturbative physics.
Conveners: D. Antonov (Heidelberg), M. Faber (TU Vienna), J. Greensite (San Francisco State U)
Focus Subsection: Emergent gauge fields and chiral fermions
Chiral Fermions and anomalous hydrodynamic effects in condensed matter systems, quantum simulators of QCD, topological phenomena in condensed matter systems.
Conveners: T. Schaefer (NC State U), V. Shevchenko (NRC Kurchatov I.)
Beyond perturbation theory gaugefixing becomes more involved due to the GribovSinger ambiguity: The appearance of additional gauge copies requires to define a procedure how to handle them. For the case of Landau gauge the structure and properties of these additional gauge copies will be investigated. Based on these properties new gauge conditions are constructed to account for these gauge copies.
The dependence of the propagators on the choice of these complete gaugefixings will then be investigated using lattice gauge theory for YangMills theory. It is found that the implications for the infrared, and to some extent midmomentum behavior, can be substantial. In going beyond the YangMills case it turns out that the influence of matter can generally not be neglected. This will be briefly discussed for various types of matter.
I will present recent progress in the calculation of nucleon resonances using the framework of DysonSchwinger and BetheSalpeter equations. The resulting mass spectra are obtained both from the threebody boundstate equation as well as its quarkdiquark approximation starting from the level of QCD's propagators and vertices. I will outline how a better understanding of these npoint functions can improve the description of the hadron spectrum. The advancements and challenges with functional methods in the extraction of resonance properties will be discussed in comparison with analogous efforts in lattice QCD. I will show results for the Roper resonance as the nucleon's first radial excitation, together with other resonances and their structure properties including electromagnetic transition form factors.
All the information about a quantum field theory is contained in the npoint functions. Once the npoint functions are computed they can be used in a next step to calculate hadron properties e.g. via the BetheSalpeter approach. On the level of threepoint functions especially the threegluon and quarkgluon vertices are of interest. The threegluon vertex captures the property of selfinteractions between gauge bosons in nonAbelian theories which is linked to confinement. On the other hand the quarkgluon vertex is crucial for the coupling of the YangMills sector to the matter sector. In this work we will discuss solutions for the threegluon and quarkgluon vertices from DysonSchwinger Equations (DSEs) and the threeparticle irreducible (3PI) formalism.
YangMills theory and 2flavour QCD are investigated with the functional renormalisation group equation in the vacuum. Starting from the perturbative parameters of QCD as only input, the effective action is calculated in a vertex expansion. The focus is put on the properties of the corresponding 1PI correlations functions as well as the relation between confinement and chiral symmetry breaking.
DysonSchwinger equations are an established, powerful nonperturbative tool for QCD. In the Hamiltonian formulation of a quantum field theory they can be used to perform variational calculations with wave functionals going beyond the Gaussian approximation. The various $n$point functions, needed in expectation values of observables like the Hamilton operator, can be thus expressed in terms of the variational kernels of our trial ansatz. Finally, the equations of motion for these variational kernels are derived by minimizing the energy density.
Section B: Light Quarks
Chiral and soft collinear effective theories; sum rules; lattice; SchwingerDyson equations; masses of light quarks; lightquark loops; phenomenology of lighthadron form factors, spectra and decays; structure functions and generalized parton distributions; exotics and glueballs; experiments.
Conveners: J. Goity (Hampton U.), B. Ketzer (Bonn U.), H. Sazdjian (IPN Orsay), N. G. Stefanis (Ruhr U. Bochum), H. Wittig (JGU Mainz)
A precise understanding of lowenergy pionnucleon interactions is central for many areas in nuclear and hadronic physics, ranging from the scalar couplings of the nucleon to the longrange part of twopionexchange potentials and threenucleon forces in Chiral Effective Field Theory. We present a calculation that combines the general principles of analyticity, unitarity, and crossing symmetry with modern highprecision data of hadronic atoms, leading to a phenomenological description of the pionnucleon amplitude with unprecedented rigor and accuracy. Consequences for the pionnucleon sigmaterm and the matching to Chiral Perturbation Theory will be discussed.
Bernhard Ketzer [Bernhard.Ketzer@cern.ch]
I will review the conditions and properties of the anomalous triangle singularity (ATS) in the transition matrix elements. For certain processes, the ATS condition can be fulfilled and will produce measureable effects in physical observables. In particular, when the ATS threshold is located within the physical regime, it may produce threshold enhancements which can mix with pole structures generated by dynamic interactions. Criteria for distinguishing the kinematically produced ATS peaks and dynamically generated poles will be discussed. Examples will be given regarding the understanding of some of those recently observed threshold states.
The low energy (below ~2 GeV) pieta channel interaction amplitude becomes an object of interest mainly because of the search for exotic mesons in just beginning to collect data detector GlueX in Jefferson Lab. Finding and interpretation of expected weak signals from these states require a comparison with a very accurate amplitude containing standard (qbar q) states i.e. a0(980) and a0(1450). The main problem in the determination of such amplitude is a total absence of data about the phases and inelasticities in the elastic and inelastic region.
In addition, it is necessary to take into account the next two coupled higher channels  KK and pieta^prime. Presented here amplitude is based on separable potential model (working very well for the scalarisoscalar pipi interactions) with only 9 free parameters. To determine such 3coupled channel amplitude, the following information has been taken into account: experimental branching ratios and positions of both a0 resonances, theoretical couplings, scattering length from ChPT and value of squared radius of the pieta form factor.
Phase shifts, inelasticities and cross sections in all single and crossed channels are presented.
Results of a sophisticated approach to a comprehensive meson phenomenology within the
rainbowladder truncated DysonSchwingerBetheSalpeter equation framework are presented
and discussed.
The exotic and nonexotic light and heavy quarkonium mass spectrum in the
spin0 and spin1 channel, as well as for tensor mesons is evaluated.
Quasiexotic counterparts of exotic quarkonia in the openflavor sector are identified and discussed.
Leptonic decay constants and orbital angular momentum decompositions are analysed and open up new perspectives on the identification
of experimentally observed states.
Section B: Light Quarks
Chiral and soft collinear effective theories; sum rules; lattice; SchwingerDyson equations; masses of light quarks; lightquark loops; phenomenology of lighthadron form factors, spectra and decays; structure functions and generalized parton distributions; exotics and glueballs; experiments.
Conveners: J. Goity (Hampton U.), B. Ketzer (Bonn U.), H. Sazdjian (IPN Orsay), N. G. Stefanis (Ruhr U. Bochum), H. Wittig (JGU Mainz)
Meson electroproduction data play an important role in our understanding of hadron structure and the dynamics that bind the basic elements of nuclear physics. Pion and kaon form factors are of particular interest as they are connected to the Goldstone modes of chiral dynamical symmetry breaking. The last decade saw a dramatic improvement in precision of charged pion form factor data and new results have become available on the pion transition form factor. Increasing the virtual photon mass in electron scattering experiments allows one to reach smaller distance scales. In this regime one becomes more and more sensitive to the partonic picture where hard and soft physics have been shown to factorize and Generalized Parton Distributions (GPDs) provide the most complete description of the nonperturbative physics. Recent data and prospects for deep exclusive pion electroproduction are presented. Experimental tests of our theoretical understanding of the reaction mechanism are shown including longitudinaltransverse separated chargedpion cross section data and ratios. The prospects to use projected charged and neutral pion data to further determine the spin, chargeparity and flavor of GPDs, including the helicityflip GPDs, are discussed.
A combination is presented of all inclusive deep inelastic cross sections previously published by the H1 and ZEUS collaborations at HERA for neutral and charged current ep scattering for zero beam polarisation. The data were taken at proton beam energies of
920, 820, 575 and 460 GeV and an electron beam energy of 27.5 GeV. The data correspond to an integrated luminosity of about 1 fb −1 and span six orders of magnitude in negative fourmomentumtransfer squared, Q2, and Bjorken x. The combined cross sections were input to QCD analyses at leading order, nexttoleading order and at nexttonexttoleading order, providing a set of parton distribution functions, HERAPDF2.0. By including jet cross sections, a precise determination of the strong coupling alpha_S is performed.
References: Eur.Phys.J.C75 (2015) 12, 580 [arxiv:1506.06042] and DESY14089 Eur.Phys.J.C75 (2015) 2, 65 [arxiv:1406.4709]
We have analysed the phenomenological dependence of the spin independent ($F_1^{p,n}$ and $F_2^{p,n}$) and the spin dependent ($g_1^{p,n}$) structure functions of the nucleon on the the Bjorken scaling variable $x$ using the unpolarized distribution functions of the quarks $q(x)$ and the polarized distribution functions of the quarks $\Delta q(x)$ respectively. The chiral constituent quark model ($\chi$CQM), which is known to provide a satisfactory explanation of the proton spin crisis and related issues in the nonperturbative regime, has been used to compute explicitly the valence and sea quark flavor distribution functions of $p$ and $n$. In light of the improved precision of the world data, the $p$ and $n$ longitudinal spin asymmetries ($A_1^p(x)$ and $A_1^n(x)$) have been calculated. The implication of the presence of the sea quarks has been discussed for ratio of polarized to unpolarized quark distribution functions for up and down quarks in the $p$ and $n$ $\frac{\Delta u^p(x)}{u^p(x)}$, $\frac{\Delta d^p(x)}{d^p(x)}$, $\frac{\Delta u^n(x)}{u^n(x)}$, and $\frac{\Delta d^n(x)}{d^n(x)}$.
We consider the predictions and estimate systematically all theoretical uncertainties
of pionphoton transition form factor using the lightcone sum rules at lowmid
momentatransfer.
The NA62 experiment at CERN collected a large sample of charged kaon decays with a highly efficient trigger for decays into electrons in 2007. The kaon beam represents a source of tagged neutral pion decays in vacuum. A measurement of the electromagnetic transition form factor slope of the neutral pion in the timelike region from ~1 million fully reconstructed pi0 Dalitz decay is presented. The limits on dark photon production in pi0 decays from the earlier kaon experiment at CERN, NA48/2, are also reported.
In this talk we present the Twohadron saturation (THS) scenario for the PVV correlator and apply it to two important processes of the low energy hadron physics: the Dalitz decay of $\pi^0$ and $\pi^0\to e^+e^$. We briefly summarize experimental and theoretical results on the rare decay $\pi^0\to e^+e^$. The notorious $3.3\,\sigma$ discrepancy between the SM prediction and the experimental value provided by KTeV collaboration is discussed in the view of a complete set of NLO QED radiative corrections. The important contribution of analytical twoloop QED corrections together with the bremsstrahlung contribution beyond the softphoton approximation are reviewed. Using the leading logarithm approximation, the possible contribution of QCD corrections is estimated. The discrepancy under discussion then reduces down to $1.8\,\sigma$. The obtained results can be also used in a theoretical calculation of the hadronic lightbylight scattering contribution to the $g2$ type experiments.
Section C: Heavy Quarks
Heavylight mesons, heavy quarkonia, heavy baryons, heavy exotics and related topics: phenomenology of spectra, decays, and production; effective theories for heavy quarks (HQET, NRQCD, pNRQCD, vNRQCD, SCET); sum rules for heavy hadrons; lattice calculations of heavy hadrons; heavyquark masses determination; experiments.
Conveners: G. Bodwin (Argonne NL), P. Pakhlov (ITEP, Moscow), J. Soto (U. Barcelona), A. Vairo (TU Munich)
We show that having at hand the analytic expression for the correlation functions allows one to study subtle effects related to isospinbreaking effects in the decay constants of heavy pseudoscalar and vector mesons. We obtain predictions for these effects in fD, fD, fB and fB mesons.
The aspects of mesons containing a single heavy quark are governed by the spin symmetry $SU(2)_s$ of the heavy quark and the chiral symmetry $SU(3)_L\times SU(3)_R$ of the light quarks. Incorporating both approximate symmetries in a single framework was achieved by defining the heavy meson chiral perturbation theory (HMChPT).
The masses of D and B mesons are analysed within this effective theory including oneloop chiral and $O(m^{1}_Q)$ corrections.
The free parameters are determined in certain linear combinations using the physical values of D meson masses, light meson masses and coupling constants.
The fitted parameters are then used to predict the masses of the full set
of the lowlying B meson states. There is a good agreement between our theoretical predictions and the available experimental data on the masses of the ground state, $J^P=0^$ and $J^P=1^$, B mesons. For the first excited, $J^P=0^+$ and $J^P=1^+$, B mesons, our results may be helpful to experimentalists looking for such states.
The mass of the bottom quark can be determined with high precision from moments of the pairproduction cross section $\sigma(e^+ e^ \to b \bar{b})$ near threshold. We present the first complete NNNLO determination from nonrelativistic sum rules, obtaining a bottomquark mass of $m_b^\text{PS}(2\,\text{GeV}) = 4.532^{+0.013}_{0.039}\,\text{GeV}$ in the potentialsubtracted scheme. For the mass in the $\overline{\text{MS}}$ scheme we find $m_b^{\overline{\text{MS}}} (m_b^{\overline{\text{MS}}}) = 4.203^{+0.016}_{0.034}\ \text{GeV}$ using the recently computed fourloop correction to the scheme conversion.
Although the main use of lattice QCD computation is to provide nonperturbative calculation of lowenergy physical quantities, it can also be used to calculate shortdistance quantities. By matching thus calculated shortdistance current correlators to corresponding perturbative calculations one can obtain the parameters appearing in the perturbation theory, such as the strong coupling constant and quark masses. We discuss about the several uses of the shortdistance current correlators.
Hadrons carrying heavy quarks, i.e. charm or bottom, are important probes of the hot and dense medium created in relativistic heavyion collisions. Heavy quarkantiquark pairs are mainly produced in initial hard scattering processes of partons. While some of the produced pairs form bound quarkonia, the vast majority hadronize into open heavy flavor particles. RHIC experiments carry out a comprehensive physics program which studies open heavy flavor and quarkonium production in relativistic heavyion collisions. The discovery at RHIC of large highpT suppression and flow of electrons from heavy quarks flavors have altered our view of the hot and dense matter formed in central Au+Au collisions at 200 GeV. These results suggest a large energy loss and flow of heavy quarks in the hot, dense matter. In recent years, the RHIC experiments installed silicon vertex trackers both in central rapidity and in forward rapidity regions, and has collected large data samples. These silicon trackers enhance the capability of heavy flavor measurements via precision tracking.
This talk summarizes the latest RHIC experiments results concerning open and closed charm and beauty heavy quark production as a function of rapidity, energy and system size, and their interpretation with respect to the current theoretical understanding on this topic.
Section D: Deconfinement
QCD at finite temperature; quarkgluon plasma detection and characteristics; jet quenching; transportation coefficients; lattice QCD and phases of quark matter; QCD vacuum and strong fields; heavyion experiments.
Conveners: C. Allton (Swansea U.), E. Iancu (CEA/DSM/Saclay), M. Janik (WUT), P. Petreczky (BNL), A. Vuorinen (U. Helsinki), Y. Foka (GSI)
Soft particle production in ultrarelativistic heavyion collisions is surprisingly well described by the "flow paradigm" which states that particles are emitted independently, according to a oneparticle probability distribution that fluctuates event to event. I review some consequences of this flow paradigm and show how it can be used to relate correlations of different orders.
Anisotropic flow studies play a crucial role in improving our understanding of the behaviour and the nature of matter created in collisions of heavy ions. The different flow harmonics ($v_n$) harmonics for identified particles can be used to constrain the initial conditions and the value of shear viscosity over entropy density ratio. These studies allow also to reveal the role of the hadronic rescattering phase in the development of flow.
In this talk I review the results from measurements of elliptic ($v_2$), triangular ($v_3$), quantrangular ($v_4$) and pentagonal ($v_5$) of identified particles from the RHIC and LHC heavyion physics programs.
General aspects of the application of hydrodynamics in theoretical description of heavyion collisions are shortly reviewed with the emphasis on the following issues: fluid variables, the form of hydrodynamic expansion, early thermalization vs. early hydrodynamization scenario, the use of the realistic equation of state, incorporation of the phase transition and preequilibrium flow, free streaming vs. hydrodynamic expansion, determination of the kinetic coefficients, quarkgluon plasma as a new state of matter with the properties determined by the hydrodynamic approach.
Observation of novel longrange collective phenomena in highmultiplicity pp and pA collisions at the LHC has opened up new opportunities of exploring QCD dynamics in a highdensity environment. Major progress in experimental and theoretical community has been made in recent years to unravel the physical origin of the observed phenomena. In this talk, I will review the experimental results including the latest pp data from the LHC run 2 in 2015. In the context of various proposed theoretical interpretations I will discuss what we have learned so far, and what are the opportunities and challenges in the future.
Anisotropic hydrodynamics is a reformulation of relativistic viscous hydrodynamics which allows one to more reliably describe nonequilibrium fluid dynamics. This is accomplished by taking into account inherent localrestframe momentumspace anisotropies at leading order. Through comparisons with recently obtained exact solutions to the Boltzmann equation, it has been shown that anisotropic hydrodynamics is the most accurate approach to modeling relativistic dissipative fluid dynamics. The main application area for anisotropic hydrodynamics has historically been in modeling the quarkgluon plasma generated in relativistic heavyion collisions, however, there have also been applications to cold atomic gases. In this talk, I will review recent progress in anisotropic hydrodynamics which have included: development of realistic (3+1)d codes with fluctuating initial conditions, implementation of latticebased equation of state, inclusion of multiple anisotropy parameters and NLO corrections, anisotropic CooperFrye freezeout, and bulk viscous effects. Finally, I will present preliminary phenomenological results together with comparisons to LHC data for particle spectra and collective flow.
Section E: QCD and New Physics
Physics beyond the Standard Model with hadronic physics precision experimental data and precision calculations.
Conveners: W. Detmold (MIT), M. Gersabeck (U. Manchester), F. J. LlanesEstrada (UC Madrid), E. Mereghetti (Los Alamos NL), J. Portoles (IFIC, Valencia)
coupling constant, nonperturbative QCD parameter, dispersive model.
If the Higgs boson discovered at the LHC is not exactly the one predicted
by the Standard Model the theory becomes strongly coupled at high energy
and vector boson scattering violates unitarity in the TeV range. This can
be regularised by the introduction of new heavy resonances. These
resonances may also couple to quark pairs and can be searched for in their
decay to vector or Higgs bosons.
The ATLAS detector at the LHC is collecting data at 13 TeV since 2015. A
search for new heavy resonances arising from WW scattering in vector boson
fusion events using these data is presented. Interference effects between
the new resonances and the Standard Model amplitude are fully taken into
account. In addition searches for heavy resonances in the decay to a pair
of bosons without tagging the initial state are shown.
The WZ boson pair production at 13 TeV is measured using the ATLAS detector. Leptonic decays of the W and Z bosons to electrons and muons are considered using 2015 and 2016 data. The differential crosssection as a function of jet multiplicity, the Zboson pT and the transverse mass of the WZ system are also measured along with the chargedependent W+Z and WZ crosssections and their ratio. Finally, the integrated fiducial crosssections ratio, measured at centerofmass energies of 13 TeV and 8 TeV, is calculated and limits on anomalous triple gauge couplings are set.
Measurements of the cross sections of the production of pairs of electroweak gauge bosons at the LHC constitute stringent tests of the electroweak sector of the Standard Model and provide a modelindependent means to search for new physics at the TeV scale.
The ATLAS collaboration has measured inclusive and differential cross sections of the production of ZZ pairs in final states with four charged leptons using data corresponding to 20.3 /fb at a centreofmass energy of 8 TeV and data corresponding to 3.2 /fb at a centerofmass energy of 13 TeV. The studies at 8 TeV are extended to the final state of two charged leptons and two neutrinos, which enhances the acceptance at high transverse momentum. These measurements are compared to calculations at NNLO in pQCD and provide constraints on new physics, by setting limits on anomalous triple gauge couplings.
The properties of the QCD axion are strictly related to the
dependence of the theory on the topological parameter theta.
We will present a determination of the topological properties of QCD for
temperatures up to around 600MeV, obtained by lattice QCD simulations
with 2+1 flavors and physical quark masses. Numerical results for
the topological susceptibility, when compared to instanton gas
computations, differ both in size and in the temperature dependence.
We will discuss the implications of such findings for axion
phenomenology.
The determination of quark masses from lattice QCD simulations requires a nonperturbative renormalization procedure and subsequent scale evolution to high energies, where a conversion to the commonly used $\overline{\rm MS}$ scheme can be safely established. We present our results for the nonperturbative running of renormalized quark masses in $N_{\rm f}=3$ QCD between the electroweak and a hadronic energy scale, where lattice simulations are at our disposal. Recent theoretical advances in combination with wellestablished techniques allows to follow the scale evolution to very high statistical accuracy, and full control of systematic effects. We close the presentation with prospects for quark mass determinations in physical units from threeflavour QCD.
The study of the couplings of the Higgs boson and of the top quark plays a preeminent role at the LHC, and could unveil the first signs of new physics. I will discuss the interplay of direct and indirect probes of certain classes of top and Higgs couplings. Including constraints from collider observables, precision electroweak tests, flavor physics, and electric dipole moments (EDMs), I will show that indirect probes are competitive, if not dominant, for both the CPeven and CPodd top and Higgs couplings we considered. I will discuss the role of theoretical uncertainties, associated with hadronic and nuclear matrix elements, and indicate targets to further improve the constraining power of EDM experiments.
Section G: Strongly Coupled Theories
Hints on the confinement/deconfinement mechanisms from supersymmetric and string theories; strongly coupled theories beyond the Standard Model; applications of nonperturbative methods of QCD to other fields.
Conveners: D. Espriu (U. Barcelona), Z. Fodor (BU Wuppertal), E. Kiritsis (APC and U. Crete), F. Sannino (CP3Origins), A. Weiler (TU Munich)
I will present recent progress on the lattice investigation of a nearly conformal gauge theory, SU(3) with 2 flavors of sextet fermions, that may realize a composite Higgs impostor scenario.
I will review some of the recent progress in determining the infrared behavior of two color gauge theory with fermions in fundamental or adjoint representation of the gauge group. Particular focus will be given to the theory with six Dirac fermions in the fundamental reptesentation.
We investigate the spectrum of the SU(2) gauge theory with
Nf = 2 flavors of fermions in the fundamental representation, in the
continuum, using Lattice simulations.
This model provides a minimal template which has been used for
different strongly coupled extensions of the Standard Model ranging from
composite (Goldstone) Higgs models to intriguing types of dark
matter candidates, such as the SIMPs.
Here we will focus on the composite Goldstone Higgs paradigm, for
which this model provides a minimal UV complete realization in terms
of a new strong sector with fermionic matter.
After introducing the relevant Lattice methods used in our
simulations, we will discuss our numerical results.
We show that this model features a SU(4)/Sp(4) ~ SO(6)/SO(5) flavor
symmetry breaking pattern, as expected, and estimate the value of its
chiral condensate.
Finally, we present our results for the mass spectrum of the lightest
spin one and zero resonances, analogue to the QCD $\rho$, $a_1$, $\sigma$,
$\eta'$, $a_0$ resonances, which are relevant for searches of new, exotic
resonances at the LHC.
We study the effect of magnetic field $B$ on the critical temperature $T_{c}$ of the confinementdeconfinement phase transition in hardwall AdS/QCD, and holographic duals of flavored and unflavored $\mathcal{N}=4$ superYang Mills theories on $\mathbb{R}^3\times \rm S^1$. For all of the holographic models, we find that $T_{c}(B)$ decreases with increasing magnetic field $B\ll T^2$, consistent with the \textit{inverse magnetic catalysis} recently observed in lattice QCD for $B\lesssim 1~GeV^2$. We also predict that, for large magnetic field $B\gg T^2$, the critical temperature $T_{c}(B)$, eventually, starts to increase with increasing magnetic field $B\gg T^2$ and asymptotes to a constant value.
The strong CP problem of QCD can be solved via the PecceiQuinn mechanism. The resulting pseudoGoldstone bosons, the axions are natural candidates for dark matter. In order to quantitatively understand axion dark matter production two important QCD inputs are required: the equation of state and the topological susceptibility at high temperatures. We determine these quantities and use them to determine the axion mass in different axion production scenarios.
I review recent work on the RoySteiner equations for pionnucleon scattering. This allows to extract the S and Pwave phase shifts in the lowenergy and subtreshold regions and a precise extraction of the much debated pionnucleon sigma term. I also discuss these results in view of recent sigma term determination from various lattice QCD collaborations.
Inclusive observables, insensitive to hadronization effects, are adequately described with the shortdistance Operator Product Expansion. Higherorder perturbative calculations and improved experimental data sets make possible performing precise tests of QCD and accurate deteminations of the strong coupling at the NNNLO. The present status will be reviewed.
The discrepancy between the measured Lamb shift in muonic hydrogen and expectations from electronproton scattering and hydrogen spectroscopy has become known as the proton radius puzzle, whose most "mundane" resolution requires a $\sim 5 \sigma$ shift in the value of the Rydberg constant. I review the status of spectroscopic and scattering measurements, recent theoretical developments, and implications for fundamental physics.
There are a number of high profile, high impact experiments planned to probe the limits of the Standard Model through precision measurements at low energies in nuclear physics environments. These experiments include searches for: direct dark matter detection through the elastic recoil of large nuclei; CPviolation manifested in permanent electric dipole moments in nucleons and nuclei; neutrinoless double betadecay of large nuclei indicating lepton number violation. The interpretation of the experimental results will require input from theoretical nuclear physics quantitatively connected to the fundamental theory of strong interactions, QCD. I will describe how lattice QCD and effective field theory can be used to make this connection and conclude with a brief survey of recent results in this vein.
Presented at Confinement XII
Precision measurements of flavour observables can provide powerful tests of many extensions of the Standard Model. I will present a review of recent heavy flavour results, focussing on places where tensions have started to appear between experimental measurements and Standard Model predictions. The talk will discuss possible explanations for these tensions and highlight areas where theoretical progress (in QCD) is needed to keep pace with increasing experimental precision.
We study the relation between quark confinement and chiral symmetry breaking in QCD.
First, we analytically derive some relations of the Polyakov loop or its fluctuations with Dirac eigenmodes for Wilson, clover and DomainWall fermions in QCD [13]. For these quantities related to confinement, the contribution from the lowlying Dirac eigenmodes is found to be negligibly small, while the modes are essential for chiral symmetry breaking.
Second, we study quark confinement and chiral symmetry breaking in holographic QCD in various spacetime dimensions.
[1] T.M. Doi, H. Suganuma and T. Iritani, Phys. Rev. D90, 094505 (2014).
[2] T.M. Doi, K. Redlich, C. Sasaki and H. Suganuma, Phys. Rev. D92, 094004 (2015).
[3] H. Suganuma, T.M. Doi and T. Iritani, Prog. Theor. Exp. Phys. 2016, 013B06 (2016).
The chiral magnetic effect (CME) is the generation of electrical current induced by chirality imbalance in the presence of magnetic field. It is a macroscopic manifestation of the quantum chiral anomaly in systems possessing charged chiral fermions. In quarkgluon plasma containing nearly massless quarks, the chirality imbalance is sourced by the topological transitions. In condensed matter systems, the chiral quasiparticles emerge in the socalled Dirac and Weyl semimetals having a linear dispersion relation. Recently, CME was discovered first in a 3D Dirac semimetal ZrTe$_5$ [Li, Kharzeev, et al arXiv:1412.6543, Nature Physics (2016) doi:10.1038/nphys3648)]. It is now observed in more than half a dozen Dirac and Weyl semimetals. 3D Dirac/Wyl semimetals have opened a fascinating possibility to study the quantum dynamics of relativistic field theory in condensed matter experiments, with potential for important practical applications.
The study of lattice gauge theories with Monte Carlo simulations is hindered by the infamous sign problem that appears under certain circumstances, in particular at nonzero chemical potential. So far, there is no universal method to overcome this problem. However, recent years brought a new class of nonperturbative Hamiltonian techniques named tensor networks, where the sign problem is absent. In previous work, we have demonstrated that this approach, in particular matrix product states in 1+1 dimensions, can be used to perform precise calculations in a lattice gauge theory, the massless and massive Schwinger model. We have computed the mass spectrum of this theory, its thermal properties and realtime dynamics. In this work, we extend our calculations to the case of two flavours and nonzero chemical potential. We are able to reliably reproduce known analytical results for this model, thus demonstrating for the first time that tensor networks can tackle the sign problem of a lattice gauge theory at finite density.
The protein folding problem, it has been claimed, is one of the
most important problems in science; Dirac stated that the problem
of life is one in theoretical physics. We argue that gauge invariance
can be employed, to develop an energy function that describes the dynamics
of a folding protein, with subatomic precision.
Section B: Light Quarks
Chiral and soft collinear effective theories; sum rules; lattice; SchwingerDyson equations; masses of light quarks; lightquark loops; phenomenology of lighthadron form factors, spectra and decays; structure functions and generalized parton distributions; exotics and glueballs; experiments.
Conveners: J. Goity (Hampton U.), B. Ketzer (Bonn U.), H. Sazdjian (IPN Orsay), N. G. Stefanis (Ruhr U. Bochum), H. Wittig (JGU Mainz)
The concept of Generalized Parton Distributions promises an understanding of the generation of the charge, spin, and energymomentum structure of hadrons by their fundamental constituents, quarks and gluons. Forthcoming measurements with unprecedented accuracy at Jefferson Lab and at CERN will presumably challenge our quantitative description of the threedimensional structure of hadrons. To fully exploit these future experimental data, new tools and models are currently being developed.
We will explain the difficulties of Generalized Parton Distribution modeling, and present some recent progresses. In particular we will describe the symmetrypreserving DysonSchwinger and BetheSalpeter framework. We will also discuss various equivalent parameterizations and sketch how to combine them to obtain models satisfying a priori all required theoretical constraints. We will explain why these developments naturally fit in a versatile software platform, named PARTONS, dedicated to the phenomenology of GPDs.
In the last few years we have had a major advance on our understanding
of the motion of partons inside nuclei. This has been achieved recognizing the role
of rapidity divergences in the factorization theorems for transverse momentum dependent cross sections (for DrellYan, Semiinclusive DIS, ee> 2 hadrons), using effective field theories, performing higher order calculations in perturbative QCD. This progress can provide us with a universal picture of QCD effects and a higher precision in current and future experiments. In this talk I try to resume the status of all this and discuss prospects.
A gobal effort is ongoing in the study of transversemomentum dependent structure functions and in generalised parton distribution functions. Both are linked to orbital angular momentum of quarks and gluons in the nucleon. Recent results from various experiments will be discussed.
Section C: Heavy Quarks
Heavylight mesons, heavy quarkonia, heavy baryons, heavy exotics and related topics: phenomenology of spectra, decays, and production; effective theories for heavy quarks (HQET, NRQCD, pNRQCD, vNRQCD, SCET); sum rules for heavy hadrons; lattice calculations of heavy hadrons; heavyquark masses determination; experiments.
Conveners: G. Bodwin (Argonne NL), P. Pakhlov (ITEP, Moscow), J. Soto (U. Barcelona), A. Vairo (TU Munich)
Electromagnetic E1 (and M1) multipole transitions have been studied since the early days of hadron spectroscopy because they allow to access heavy quarkonium states which are below openflavour threshold. Moreover, they are interesting by themselves because they are an important tool to check particular regions of the hadrons' wave function and thus to determine their internal structure and dynamics.
From a theoretical point of view, electromagnetic transitions between heavy quarkonium states have been treated for a long time by means of potential models using nonrelativistic reductions of phenomenological interactions. However, the progress made in effective field theories (EFTs) for studying heavy quarkonia and the new large set of accurate experimental data taken in the heavy quark sector by $B$factories (BaBar, Belle and CLEO), $\tau$charm facilities (CLEOc, BESIII) and even protonproton colliders (CDF, D0, LHCb, ATLAS, CMS) ask for a systematic and modelindependent analysis.
This contribution aims to present the first numerical determination of the $2\,{}^{3}P_{J}\to 1{}^{3}S_{1}\gamma$ ($\chi_{bJ}(1P)\to \Upsilon(1S)\gamma$) decay rates within the lowenergy EFT called potential NRQCD (pNRQCD). We assume that the heavy mesons involved in the studied reactions lie in the weakcoupling regime of pNRQCD and thus a full perturbative calculation can be performed. Relativistic corrections of relative order $v^{2}$ to the leading electric dipole operator are included. The analysis separates those contributions that account for the electromagnetic interaction terms in the pNRQCD Lagrangian, which are $v^{2}$ suppressed, and those that account for quarkonium state corrections of relative order $v^{2}$. Within the last ones, corrections come from higherorder potentials ($1/m$ and $1/m^2$ terms), and from higher Fock states which account for the coupling of the quarkantiquark state to other lowenergy degrees of freedom and thus demand nonperturbative input.
Belle, a generalpurpose detector operated at the KEKB electronpositron
Bfactory at KEK, Japan, collected the world largest integrated luminosity
at the peak of the $\Upsilon(4S)$ meson as well as in a scan of the
centerofmass energy range from 10.63 to 11.05 GeV.
We describe recent results on various bottomonium states studied 
mass and width measurements of the $\Upsilon(5S)$ and
$\Upsilon(6S)$ mesons, update of the $\eta_b(1S)$ and $h_b(1P)$ parameters,
new investigation of the exotic $Z_b(10610)$ and $Z_b(10650)$ states.
Numerical recovering of the spectrum and wave function of a twobody fermionic relativistic potential system.
Estimation in this framework of the widths and branching ratios of some heavy mesons radiative decays.
We use nonlinear field transformations for nonrelativistic fields to implement Poincare invariance in low energy effective theories for QCD. In these transformations we include all terms allowed by the explicit symmetries of the effective theory, but exploit the freedom to remove some of them through field redefinitions. By requiring the invariance of the Lagrangian under these transformations, relations between Wilson coefficients for both theories are derived. The calculations are presented up to the leading order in the expansion parameter. The possibility of applying this method to other types of effective theories as well as its implication will also be discussed.
We derive an analytical expression for the chromopolarizability of bottomonium states using the framework of potential nonrelativistic QCD. Next, using the QCD trace anomaly we obtain the twopion production amplitude for the chromopolarizability operator and match the result to a chiral effective field theory for bottomonium states and pions as degrees of freedom. In this chiral effective field theory we compute longrange properties of bottomonium states such as the leading chiral logarithm correction to the mass of the 1S bottomonium and derive the van der Waals potential between two bottomonium states. Finally, we discuss the perspectives of using the developed chiral effective theory to evaluate twopion decay amplitudes of bottomonium states.
Section D: Deconfinement
QCD at finite temperature; quarkgluon plasma detection and characteristics; jet quenching; transportation coefficients; lattice QCD and phases of quark matter; QCD vacuum and strong fields; heavyion experiments.
Conveners: C. Allton (Swansea U.), E. Iancu (CEA/DSM/Saclay), M. Janik (WUT), P. Petreczky (BNL), A. Vuorinen (U. Helsinki), Y. Foka (GSI)
Due to the nonAbelian nature of QCD and the existence of the 3gluon coupling, the wavefunction of a high energy hadron at smallx is dominated by gluons (with x the longitudinal momentum fraction of a parton). The occupation numbers for these soft gluons increase rapidly with decreasing x and eventually saturate to their maximal allowed value, in a region where the coupling is still weak. The most suitable way to study this phenomenon of parton saturation, is to probe the hadron with a small color dipole, and the ensuing evolution equation for the scattering amplitude is the BalitskyKovchegov (BK) equation, with its NLO version derived a few years ago. We show that the NLO BK eqaution leads to unphysical solutions, we identify the reason for the large and negative NLO corrections and we resum the respective terms to all orders. The emergent resummed evolution equation can be used to address many phenomenological aspects in hadronic, and in particular heavyion, collisions.
A full understanding of the spacetime evolution of the QCD matter created in a heavy ion collision requires understanding the properties of the initial stages. In the weak coupling picture these are dominated by classical gluon fields, whose properties can also be studied via the scattering of dilute probes off a high energy hadron or nucleus. A particular challenge is understanding small systems, where LHC data is also showing signs of collective behavior. We discuss some recent results of on the initial matter production and thermalization in heavy ion collisions, in particular in the gluon saturation framework.
The combination of multiple particle identification systems along with the excellent tracking capabilities makes ALICE a unique tool for the measurement of light flavor hadron production over a broad transverse momentum ($p_{\rm T}$) range.
The production of $\pi^{\pm}$, $\mathrm{K}^{\pm}$, ${\rm K}^{0}_{S}$, $\rm p$,
$\rm\overline{p}$, $\Lambda$, $\bar{\Lambda}$, $\Xi^$, $\overline{\Xi}^+$, $\Omega^$ and $\overline{\Omega}^+$ hadrons measured at midrapidity in protonproton collisions at $\sqrt{s} =$ 7 TeV as a function of chargedparticle multiplicity will be presented.
The observed multiplicity dependence of $p_{\rm T}$spectra and their ratios is reminiscent of the behavior in PbPb collisions, where the spectral shapes are interpreted in the context of a hydrodynamical evolution of the colliding system.
Moreover, the ratios of strange hadron production to the pion production are seen to increase with multiplicity, which is not the case for nonstrange hadrons. The strength of the increase scales with the number of the strange valence quarks.
Commonly used MonteCarlo models (e.g. PYTHIA8, EPOS LHC) are not able to reproduce our observations for pp collisions.
The talk will also include new ALICE results on light flavor hadron production in pp collisions at $\sqrt{s} =$ 13 TeV.
We discuss the importance of initial state effects with regard to the theoretical understanding of long range azimuthal correlations observed in highmultiplicity p + p and p + A collisions at RHIC and the LHC. Starting with a brief overview of different effects, we perform a systematic comparison of initial state calculations with experimental data and briefly discuss progress towards developing a unified picture of initial state and final state effects.
Identified hadron spectra are considered to be sensitive to transport properties of strongly interacting matter produced in highenergy nucleusnucleus collisions.
π0 and η mesons in ALICE are identified via their twophoton decays by using calorimeters and the central tracking system. In the latter, photons are measured via their conversion to electronpositron pairs on the material of the inner ALICE barrel tracking detectors.
The measured production spectra in pp pPb and PbPb collisions at mid rapidity and over a wide pT range will be presented in the available LHC energies of Run I.
The resulting nuclear modification factor RAA at different centrality classes shows a clear pattern of strong suppression in the hot QCD medium with respect to pp collisions.
Comparison of the ALICE results on neutral mesons with lowerenergy experiments will also be discussed.
Section D: Deconfinement
QCD at finite temperature; quarkgluon plasma detection and characteristics; jet quenching; transportation coefficients; lattice QCD and phases of quark matter; QCD vacuum and strong fields; heavyion experiments.
Conveners: C. Allton (Swansea U.), E. Iancu (CEA/DSM/Saclay), M. Janik (WUT), P. Petreczky (BNL), A. Vuorinen (U. Helsinki), Y. Foka (GSI)
I discuss calculations of the Polyakov loop and of Polyakov loop correlators using lattice gauge theory.
I briefly review recent calculations (since Conf. 2014) of the Polyakov loop and static quark correlators.
I cover in detail results in QCD with 2+1 flavors and almost physical quark masses using the highly improved staggered quark action (HISQ).
I examine the short and longdistance regimes of the correlators and discuss the colorscreening in the thermal medium.
I elucidate how the Polyakov loop and related observables behave in the crossover region and how these observables probe the deconfinement aspects of the crossover.
I study the onset of weakcoupling behavior at high temperatures and short distances.
The magnitude of axial U(1) symmetry breaking is believed to affect the nature of phase transition in QCD with two light quark flavors. I review the recent studies on the fate of axial U(1) in finite temperature QCD using lattice techniques. Most of them investigate the eigenvalue spectrum of the fermion Dirac operator in QCD. The current understanding from majority of these studies is that the axial U(1) is not effectively restored near Tc, the chiral crossover transition temperature. Studying the eigenvalue spectrum also gives us rich insights on the nature and interactions between the topological objects in QCD. Specifically the nearzero eigenmodes are observed to persist even at 1.5 Tc, and are primarily responsible for U(1) breaking. The nearzero eigenmodes are localized unlike those in the bulk, with a mobility edge similar to a MottAnderson like system. The possible microscopic origins of the nearzero mode spectra in QCD would be discussed in detail. At 1.5 Tc, its origin can be traced back to the dilute instanton gas ensemble. Consequences of these findings for finite temperature QCD and axion cosmology would be further discussed in this talk.
We will present recent results regarding chiral symmetry restoration and other hadronic properties at finite temperature. In particular, we will discuss the interpretation of the temperature dependence of lattice screening masses through Ward identities relating pseudoscalar susceptibilities and quark condensates. Such identities are derived for two and three flavours and studied within the $SU(2)$, $SU(3)$ and $U(3)$ frameworks of Chiral Perturbation Theory, including axial anomaly and $\eta'$ corrections. We will also examine chiral degeneration patterns and the role of the $f_0(500)$ or $\sigma$ state in the saturation of the scalar susceptibility, where our results are consistent with lattice data. The $f_0(500)$ thermal state is generated dynamically from pion scattering and thermal unitarity, both within unitarized ChPT and in other schemes such as that with large number of Goldstone Bosons. Aspects regarding external magnetic fields could also be discussed. Recent references: JHEP 1603 (2016) 186, Phys.Rev. D93 (2016) no.3, 036001.
At zero temperature nucleons and their parity partners have nondegenerate
masses due to spontaneous breaking of chiral symmetry.
However, chiral symmetry is expected to be restored at sufficiently high temperature,
in particular when going from the hadronic to the quarkgluon plasma (QGP) phase,
implying that the parity partners should become degenerate.
We study the nucleon (spin 1/2) and Delta (spin 3/2) baryons in both
parity sectors for a range of temperatures in the confined and QGP phases.
Using anisotropic $N_f = 2+1$ flavour simulations, we analyse the correlation functions and the spectral functions
using respectively exponential fits and the Maximum Entropy Method.
We find a clear sign of parity doubling for both baryons in the QGP phase:
the parity state masses become degenerate and
their corresponding correlators become essentially identical.
A novel approach to identify the geometrical (anti)clusters formed by the Polyakov loops of the same sign and to study their properties in the lattice SU(2) gluodynamics is developed. The (anti)cluster size distributions are analyzed for the lattice coupling constant $\beta$=[2.3115; 3]. The found distributions are similar to the ones existing in 2 and 3dimensional Ising systems [1]. Using the suggested approach, we explain
the phase transition in SU(2) gluodynamics at $\beta=2.52$ as a transition between two liquids during which one of the liquid droplets (the largest cluster of a certain Polyakov loop sign) experiences a condensation, while another droplet (the next to the largest cluster of opposite Polyakov loop sign) evaporates. The clusters of smaller sizes form two accompanying gases, which behave oppositely to their liquids. The liquid drop formula is used to analyze the distributions of the gas (anti)clusters and to determine their bulk, surface and topological parts of free energy. Surprisingly, even the monomer multiplicities are reproduced with high quality within such an approach. The behavior of surface tension of gaseous (anti)clusters is studied. It is shown that this quantity can serve as an order parameter of the deconfinement phase transition in SU(2) gluodynamics. Moreover, the critical exponent $\beta$ of surface tension coefficient of gaseous clusters is found in the upper vicinity of critical temperature. Its value coincides with the one found for 3dimensional Ising model within error bars. The Fisher topological exponent
$\tau$ of (anti)clusters is found to have the same value 1.806 $\pm$ 0.008, which agrees with an exactly solvable model of the nuclear liquidgas phase transition [2] and disagrees with the Fisher droplet model [3], which may evidence for the fact that the SU(2) gluodynamics and the model [2] are in the same universality class.
[1] L. Moretto et al., Phys. Rev. Lett. 94, 202701 (2005).
[2] V. Sagun, A. Ivanytskyi, K. Bugaev and I. Mishustin, Nucl. Phys. A 924, 24 (2014).
[3] M. E. Fisher, Physics 3, 255 (1967).
Section F: Nuclear and Astroparticle Physics
Nuclear matter; nuclear forces; quark matter; neutron and compact stars.
Conveners: M. Alford (Washington U. in St.Louis), D. Blaschke (U. Wroclaw), T. Cohen (U. Maryland), L. Fabbietti (TU Munich), A. Schmitt (U Southampton)
The Symmetry Energy is a fundamental ingredient of the nuclear matter Equation Of State.
The ellipticflow ratio of neutrons with respect to protons or light complex particles in
reactions of heavyions at prerelativistic energies has been proposed as an observable sensitive to the strength of the Symmetry Energy at suprasaturation densities.
The results obtained from the existing FOPI/LAND data for Au+Au collisions at 400
MeV/nucleon in comparison with the UrQMD model indicate a moderately soft symmetry energy
but suffer from a considerable statistical uncertainty [1]; these results were confirmed by an independent analysis based on Tubingen QMD [2].
A new experiment, carried out at the GSI laboratory by the ASYEOS collaboration [3], has given a more stringent constraint for the nuclear symmetry energy at suprasaturation densities.
Moreover, future plans for extending these studies at higher densities, also by using Radioactive Ion Beams, will be discussed.
Talk presented on behalf of the AYSEOS and NewCHIM collaborations
[1] P. Russotto et al., Phys. Lett. B 697 (2011) 471.`
[2] M.D. Cozma, Phys. Lett. B 700, 139 (2011); M.D. Cozma et al., Phys. Rev. C 88, 044912
(2013).
[3] P. Russotto et al., Eur. Phy. J A 50, 38 (2014); P. Russotto et al., submitted to Phys. Rev. C (2016).
HADES at SIS18 is currently the only experiment studying properties of strongly interacting matter by means of rare and penetrating probes using proton and heavy ion beams in a few AGeV energy range. The study of system size dependence has been recently completed with Au+Au collisions at 1.23 AGeV. The measurements provide a results on kaons, strange resonances, including the first at such low energies data on double strange Ksi(1321), and on low mass dielectrons. The particle production have been measured over large range of rapidities and transverse momenta allowing for extrapolation to full solid angle and for comparisons to thermal , statistical hadronization models and transport models. The results, in particular an unexpected large ratio of K/phi and the cascade, will be presented and discussed. The results on dielectron production points clearly to a significant contribution of thermal emission from hot a dense phase of the collision. Characteristic features of the radiation will be presented and compared to those obtained and higher energies (RHIC/SPS).
The AMADEUS experiment deals with the investigation of the lowenergy kaonnuclei hadronic interaction at the DAΦNE collider at LNFINFN, which is fundamental to solve longstanding questions in the nonperturbative strangeness QCD sector. AMADEUS step 0 consisted in the reanalysis of 2004/2005 KLOE data, exploiting $K^−$ absorptions in H, ${}^4$He, ${}^9$Be and ${}^{12}$C, leading to the first invariant mass spectroscopy study with very low momentum (100MeV) inflight $K^−$ captures. With AMADEUS step 1 a dedicated pure Carbon target was implemented in the central region of the KLOE detector, providing a high statistic sample of pure atrest $K^−$ nuclear interaction.
The results obtained in the analyses of the hyperonpion correlated events, searching for the resonant shapes of Y$^*$ states, and the analyses of hyperonproton, deuteron, and triton correlations, searching for possible $K^$multi nucleon bound states, will be presented.
The inmedium modification of hadron properties is the main field of study for the strangeness sector in the nonperturbative lowenergy region of QCD.
The behaviour of strange hadrons at extreme densities are of capital importance for the description of the nuclear equation of state and the evaluation of the strangeness component in the core of the neutron stars.
The study of hyperonnucleon(s) and hyperonpion correlations following K$^$ nuclear absorption in $^4$He and $^{12}$C were investigated with the KLOE drift chamber and the results will be presented. To this end, KLOE [1] data (from 200420052012) was analyzed using the detector itself as an active target.
The $\Sigma^0$p final state has been analyzed exclusively for the first time [2].
The results include yield per stopped kaon for the simplest two nucleon "quasifree" absorption, ratios for the twonucleon vs threenucleon process, and a systematic search for a ppK$^$ bound state.
The existence of such objects, whose experimental detection has been claimed several times recently, also in absorption experiments, would open the possibility for the formation of very dense baryonic matter implying a deep attractive value for the antikaonnucleon potential.
The analysis of the $\Lambda(\Sigma^0)\pi$ channel from absorptions in $^4$He will be presented as well.
The data have been interpreted within a theoretical phenomenological model which allows to quantify the role played by the resonant $\Sigma$(1385) formation, allowing to extract the module of the nonresonant K$^−$n $\rightarrow \Lambda \pi$ amplitude (∼ 33 MeV/c$^2$ below threshold).
[1] F. Bossi et al. Riv. Nuovo Cimento 31 (2008) 10.
[2] O. Vazquez Doce et al., Physics Letters B 758 (2016) 134.
Section G: Strongly Coupled Theories
Hints on the confinement/deconfinement mechanisms from supersymmetric and string theories; strongly coupled theories beyond the Standard Model; applications of nonperturbative methods of QCD to other fields.
Conveners: D. Espriu (U. Barcelona), Z. Fodor (BU Wuppertal), E. Kiritsis (APC and U. Crete), F. Sannino (CP3Origins), A. Weiler (TU Munich)
It is based on https://arxiv.org/abs/1511.03868 as well as work which should appear soon.
In order to obtain a better understanding of QCD as well as possible strongly coupled extensions of the Standard Model it is important that we reliably can calculate anomalous dimensions of certain composite operators at fixed points. We show how to consistently calculate the mass anomalous dimension order by order in perturbation theory in a scheme independent manner. We compare our calculation to exact known results in supersymmetric QCD and find that they can astonishingly well be approximated by a few loops computation. We then calculate the mass anomalous dimension in QCD and discuss its implications for building realistic models of beyond the Standard Model.
I will start by an introduction to holographic QCD, concentrating on bottomup models where the backreaction of quarks to gluon dynamics is fully included (VQCD models). The physics of theta angle and axial anomaly can be consistently included in such models. At small quark mass the models agree with effective field theory. I show how the GellMannOakesRenner relation for the mass of the pion and the WittenVeneziano relation for the mass of the eta prime meson arise.
Section A: Vacuum Structure and Confinement
Mechanisms of quark confinement (vortices, monopoles, calorons...) and the structure of the vacuum in nonAbelian gauge theories. Chiral symmetry breaking, and the Dirac spectrum in the lowmomentum region. Studies of ghost and gluon propagators. Confining strings and flux tubes, their effective actions. Renormalons and power corrections. Interface between perturbative and nonperturbative physics.
Conveners: D. Antonov (Heidelberg), M. Faber (TU Vienna), J. Greensite (San Francisco State U)
Focus Subsection: Emergent gauge fields and chiral fermions
Chiral Fermions and anomalous hydrodynamic effects in condensed matter systems, quantum simulators of QCD, topological phenomena in condensed matter systems.
Conveners: T. Schaefer (NC State U), V. Shevchenko (NRC Kurchatov I.)
QCD thermodynamics in strong magnetic fields shows some unexpected features like inverse catalysis, which have been revealed mainly through lattice studies. Many effective descriptions, on the other hand, use Landau levels or approximate the system by just the lowest Landau level (LLL). Analyzing lattice configurations we ask whether such a picture is justified. We find the LLL to be separated from the rest by a spectral gap in the twodimensional Dirac operator and look for the corresponding signals in four dimensions. We determine to what extent the quark condensate is LLL dominated at various magnetic fields and temperatures.
We study $N_f=2$ lattice QCD with improved Wilson fermions at imaginary chemical potential $\mu_I.$ Simulations are made in the deconfinement phase at few values of $\mu_I/T$ to study RobergeWeiss phase transitions at $\mu_I/T = \pm \pi/3$ and $\pi$. We measure spectrum of overlap Dirac operator in background of equilibrium configurations with variable $\mu_I/T$. Numerical evidence is presented to show that RobergeWeiss transitions are related to changes in the spectrum gap. We suggest explanation of our numerical results in terms of dyons.
We show how the increase in the Instantondyon density can explain both Confinement and Chiral symmetry breaking. We simulate an ensemble of 64 interacting Instantondyons for 2 colors and 0 or 2 quark flavors. We find that at low temperatures, the high density of dyons prefer a symmetric density, which leads to the confining value of the Polyakov Loop. At the same time the Chiral condensate is highly sensitive to the Polyakov Loop. As the Polyakov Loop gets close to the confining value, the Chiral condensate develops a nonzero expectation value, thus breaking Chiral symmetry.
The renormalization group procedure for effective particles (RGPEP) has been
developed during the last years as a nonperturbative tool for constructing
boundstates in quantum field theories [1]. It stems from the similarity
renormalization group procedure (SRG) [2] and introduces the concept of effective
particles, which differ from the pointlike canonical, bare ones by
having a finite size $s$. The effective particles in the Fock space build
the hadronic eigenstates of a family of effective Hamiltonians H_s depending
on the size s as the RGPEP scale parameter. We apply the RGPEP
to QCD using an expansion in powers of the coupling constant up to third order.
The Hamiltonian running coupling, $g_s$, is extracted from the interaction terms
in $H_{s}^{QCD}$ [3]. We thus demonstrate that the RGPEP passes the test of describing
asymptotic freedom, which is a precondition for any approach aiming at using
QCD for explaining hadrons in the Minkowski spacetime, especially for tackling
nonperturbative issues, such as the ones that emerge when one allows effective
gluons to have masses [2]. Applications of this method beyond the leading order are under way and it is hoped that the interaction terms relevant to understanding of confinement will be gradually determined.
[1] S. D. Glazek, Acta Phys. Polon. B42 (2011) 1933; Acta Phys. Polon. B43 (2012) 1843.
[2] K. G. Wilson, T. S. Walhout, A. Harindranath, W.M. Zhang, R. J. Perry, and S. D. Glazek, Phys. Rev. D49 (1994) 67206766
[3] M. GomezRocha and S. D. Glazek, Phys. Rev. D92 (2015) 065005.
The confinement and the gribov ambiguity are two nonperturbative phenomena of great importance in QCD. Abelian dominance, a signature to the confinement, is mostly studied in Maximal abelian gauge which is Abelian projection. The Gribov ambiguity exists in various gauges. Algebraic gauges are more likely to be ambiguity free but are not compatible with the boundary conditions i.e.,the ambiguity continues to exist on a compact manifold. In general, algebraic gauges are not Lorentz invariant, which is their fundamental flaw. We consider a quadratic gauge, which is an algebraic gauge. It is Lorentz invariant and does not fall into the class of Abelian projection. We show that the gauge has two strong signatures of the confinement. We then provide an example of spherically symmetric gauge field and prove that with a proper boundary condition on the configuration, this gauge removes the ambiguity on a compact manifold $\mathbb{S}^3$. Thus, It is more suitable for the nonperturbative phenomena in QCD.
Section B: Light Quarks
Chiral and soft collinear effective theories; sum rules; lattice; SchwingerDyson equations; masses of light quarks; lightquark loops; phenomenology of lighthadron form factors, spectra and decays; structure functions and generalized parton distributions; exotics and glueballs; experiments.
Conveners: J. Goity (Hampton U.), B. Ketzer (Bonn U.), H. Sazdjian (IPN Orsay), N. G. Stefanis (Ruhr U. Bochum), H. Wittig (JGU Mainz)
While QCD is the theory underlying hadronic physics, much of our intuition about hadronic states has been developed in the context of the constituent quark model. Exotic states—ones that cannot be described in the simplest version of the quark models with mesons as a quarkantiquark state and baryons as a three quark state—are important since they clarify the limitation of the quark model as a description of QCD. Recently, there has been considerable excitement in the spectroscopy of hadrons containing heavy quarks: pentaquarks containing a charm and anticharm quarks have been discovered and there is strong evidence that at least some of the observed X, Y, Z states are exotic tetraquarks. However, the question of whether exotics composed of light quarks exist remains murky. This talk uses the theoretical perspective of large Nc QCD to focus on the possibility of light quark exotics. A world where the number of colors is large simplifies many of the issues that make the phenomenology of light quark states so complicated. The status of light quark exotics at large Nc will be briefly reviewed. A key result stressed in this talk is that there exists a variant of the large Nc limit in which quarks are in the twoindex symmetric representation of color. In this limit, tetraquarks composed of light quarks are shown to exist as narrow resonant states. Minimally, this proves that there is nothing generic in the structure of gauge theories that prevents lightquark tetraquarks from existing.
The method of QCD sum rules is based on the extraction of hadron observables (decay constants, form factors, etc) from the correlation functions of the appropriate quark currents. Because of the properties of the correlation functions containing the exotic multiquark (i.e. fourquark, fivequark) currents, the contribution of the exotic multiquark hadrons to these correlation functions emerge only at order alpha_s and higher; the leadingorder diagrams do not contain the contributions of the exotic multiquark states. Respectively, for the analysis of the exoticstates properties within QCD sum rules, the knowledge of the radiative corrections to the correlations functions is mandatory.
The dispersive approach to QCD, which extends the applicability range of
perturbation theory towards the infrared domain, is applied to the study
of the hadronic vacuum polarization function and related quantities. This
approach merges the intrinsically nonperturbative constraints, which
originate in the kinematic restrictions on the relevant physical
processes, with corresponding perturbative input. The obtained hadronic
vacuum polarization function agrees with pertinent lattice simulation
data. The evaluated hadronic contributions to the muon anomalous magnetic
moment and to the shift of the electromagnetic fine structure constant
conform with recent estimations of these quantities.
[1] A.V.Nesterenko, J. Phys. G42, 085004 (2015).
[2] A.V.Nesterenko, Phys. Rev. D88, 056009 (2013).
[3] M.Baldicchi, A.V.Nesterenko, G.M.Prosperi, and C.Simolo,
Phys. Rev. D77, 034013 (2008).
[4] A.V.Nesterenko and J.Papavassiliou, J. Phys. G32, 1025 (2006).
A review of familiar results of the threepoint Green functions of currents in the oddintrinsic parity sector of QCD is presented. Such Green functions include very wellknown examples of $VVP, VAS$ or $AAP$ correlators. We also present new results for $VVA$ and $AAA$ Green functions that have not yet been studied extensively in the literature before, more importantly with a phenomenological study and a discussion of the highenergy behaviour and its relation to the fourquark condensate.
The Quantum Chromodynamics (QCD) coupling, αs, is not a physical observable of the theory since it depends on conventions related to the renormalization procedure. We introduce a definition of the QCD coupling, denoted by αˆs, whose running is explicitly renormalization scheme invariant. The scheme dependence of the new coupling αˆs is parameterized by a single parameter C, related to transformations of the QCD scale Λ. It is demonstrated that appropriate choices of C can lead to substantial improvements in the perturbative prediction of physical observables. As phenomenological applications, we study e+e− scattering and decays of the τ lepton into hadrons, both being governed by the QCD Adler function, as well as the scalar correlation function.
The
dilepton invariant mass spectra and branching ratios of the single and double Dalitz decays
$\mathcal{P}\to\ell^{+}\ell^{}\gamma$ and $\mathcal{P}\to\ell^{+}\ell^{}\ell^{+}\ell^{}$
($\mathcal{P}=\pi^{0}, \eta, \eta^{\prime}$; $\ell=e$ or $\mu$) are predicted by means of a
datadriven modelindependent approach based on the use of rational approximants applied to
$\pi^{0}, \eta$ and $\eta^{\prime}$ transition form factor experimental data in the spacelike region.
Section B: Light Quarks
Chiral and soft collinear effective theories; sum rules; lattice; SchwingerDyson equations; masses of light quarks; lightquark loops; phenomenology of lighthadron form factors, spectra and decays; structure functions and generalized parton distributions; exotics and glueballs; experiments.
Conveners: J. Goity (Hampton U.), B. Ketzer (Bonn U.), H. Sazdjian (IPN Orsay), N. G. Stefanis (Ruhr U. Bochum), H. Wittig (JGU Mainz)
The nonperturbative nature of quantum chromodynamics (QCD) has historically left a gap in our understanding of the connection between the fundamental theory of the strong interactions and the rich structure of experimentally observed phenomena. For the simplest properties of stable hadrons, this is now circumvented by utilizing lattice QCD (LQCD). In this talk I outline a path towards a rigorous determination of fewhadron observables from LQCD. I illustrate the power of the methodology by presenting recently determined scattering amplitudes in the lightmeson sector and discuss their resonance content.
Numerical Lattice QCD calculations are necessarily performed in a finite volume and with Euclidean time. For scattering and transition amplitudes these constraints have important consequences. In particular, it is not possible to directly access such amplitudes from numerically determined Euclidean correlators. In the past decades, great progress has been made to overcome this limitation by using finite volume as a tool rather than an artifact, and deriving nonperturbative relations between the finite and infinitevolume theories. I will review recent developments in this work with particular focus on threehadron final states.
We calculate the neutron electric dipole moment within the framework of lattice QCD. In particular we
analyze configurations produced with $N_f=2+1+1$ twisted mass fermions with light quark mass which
corresponds to pion mass of 370 MeV. We do so by extracting the $CP$odd form factor $F_3$ at the limit of
zero momentum transfer and at small values of the $\theta$ vacuum angle. The zero momentum limit is
realized via fitting the momentum dependence by a dipole fit as well as using position space methods.
The computation of $F_3$ requires the calculation of the topological charge. We measure the field
theoretical topological charge via cooling and the gradient flow using the Wilson, Symanzik treelevel
improved and Iwasaki actions. Our analysis yields a value for the neutron electric dipole moment of
−0.045(6)(1) e·fm in units of $\theta$.
We explore the ground state energy of pseudoscalar charged and neutral mesons as a function of external magnetic field in SU(3) lattice gauge theory. We calculate the dipole magnetic polarizabilities and hyperpolarizabilities of charged and neutral pseudoscalar pi and K mesons. It was found that the magnetic polarizability of charged pion agrees with the experimental prediction of COMPASS collaboration.
Studies of multibaryon systems present a formidable challenge to lattice QCD.
The Hdibaryon represents the simplest multibaryon system and yet in the current lattice calculations at unphysical quark masses no conclusive results can be seen regarding its binding energy.
One of the contributing factors could be the inability to reliably extract the spectrum of states on the lattice.
Using the stateofart spectroscopy method of distillation, we attempt a detailed lattice calculation of the spectrum of twobaryon states in the Hdibaryon channel.
The calculations are performed at several pion masses of 450 and 1000 MeV.
The method of distillation allows for the construction of a large basis of operators, which is crucial for reliably extracting the spectrum.
A comparison with earlier calculations will also be presented.
Section C: Heavy Quarks
Heavylight mesons, heavy quarkonia, heavy baryons, heavy exotics and related topics: phenomenology of spectra, decays, and production; effective theories for heavy quarks (HQET, NRQCD, pNRQCD, vNRQCD, SCET); sum rules for heavy hadrons; lattice calculations of heavy hadrons; heavyquark masses determination; experiments.
Conveners: G. Bodwin (Argonne NL), P. Pakhlov (ITEP, Moscow), J. Soto (U. Barcelona), A. Vairo (TU Munich)
The LHCb experiment is designed to study the decays and properties of heavy flavoured hadrons produced in the forward region from pp collisions at the CERN Large Hadron Collider. It has recorded the world’s largest data sample of beauty and charm hadrons, enabling precise studies into the production and decay of such particles. $\eta_c$ production has been studied in B decays and in prompt production. For the first time its production crosssection has been measured in pp collisions. For the $\eta_c(2S)$ the decay into $p\bar{p}$ is observed for the first time. We report latest results of those measurements.
We analyze the first measurement of $\eta_c$
production, performed by the LHCb Collaboration, in
the nonrelativisticQCD (NRQCD) factorization framework
at nexttoleading order (NLO) in the
strongcoupling constant $\alpha_s$ and the relative velocity v
of the bound quarks including the feeddown
from $h_c$ mesons. Converting the longdistance matrix elements (LDM
Es) extracted by various groups from $J/\psi$
yield and polarization data to the $\eta_c$
case using heavyquark spin symmetry, we find that
the resulting NLO NRQCD predictions greatly overshoot the L
HCb data, while the colorsinglet model provides an excellent description
Section D: Deconfinement
QCD at finite temperature; quarkgluon plasma detection and characteristics; jet quenching; transportation coefficients; lattice QCD and phases of quark matter; QCD vacuum and strong fields; heavyion experiments.
Conveners: C. Allton (Swansea U.), E. Iancu (CEA/DSM/Saclay), M. Janik (WUT), P. Petreczky (BNL), A. Vuorinen (U. Helsinki), Y. Foka (GSI)
Based on arXiv:1410.6448, arXiv:1512.06445 and ongoing works
We explain the approach to thermal equilibrium of strongly coupled nonconformal plasmas using the AdS/CFT correspondence. The theories we study are the holographic duals to Einstein gravity coupled to a scalar with an exponential potential. The coefficient in the exponent, X, is the parameter that controls the deviation from the conformally invariant case. For these models we obtain analytic solutions for the plasma expansion in the latetime limit, under the assumption of boostinvariance, and we determine the scaling behaviour of the energy density, pressure, and temperature as a function of time, which is found to agree with the hydrodynamical expectation. We find that the temperature decays as a function of proper time as $T \sim τ^{−s/4}$ with the exponent s determined in terms of the nonconformality parameter X as $s = 4(1−4X$2)/3$.
Using the AdS/CFT correspondence, phenomenological models based on fivedimensional EinsteinDilaton gravity can be constructed which give a realistic description of several nonperturbative properties of YangMills theory at thermal equilibrium. These models can also be used to describe timedependent and outofequilibrium processes, and to compute observables related to heavy quark diffusion and energyloss in the QuarkGluon Plasma. In this talk I will discuss quark diffusion and energyloss in the context of holography, pointing out the main features that emerge in nonconformal models and that can be searched in heavyion hydrodynamic simulations.
Section D: Deconfinement
QCD at finite temperature; quarkgluon plasma detection and characteristics; jet quenching; transportation coefficients; lattice QCD and phases of quark matter; QCD vacuum and strong fields; heavyion experiments.
Conveners: C. Allton (Swansea U.), E. Iancu (CEA/DSM/Saclay), M. Janik (WUT), P. Petreczky (BNL), A. Vuorinen (U. Helsinki), Y. Foka (GSI)
Heavy quarkonium presents a unique observable for the study of the quarkgluon plasma in relativistic heavyion collisions. While Bottomonium is expected to act as a test particle traversing the medium in the collision center, recent measurements of finite $J/\psi$ flow by the ALICE collaboration hint at the participation of the charm quarks in the collectivity of the bulk.
Here we present recent results on the inmedium properties of kinetically thermalized heavy quarkonium obtained using lattice QCD methods. Particular emphasis is placed on the computation of spectral functions either from lattice effective field theory approaches such as NRQCD [1], or via a complex realtime potential extracted from Wilson line correlators on the lattice [2]. Consequences for phenomenology e.g. for the J/$\psi$ / $\psi$' ratio [3], as well as $\chi_c$(nP) feeddown [4] are discussed.
[1] see e.g. S.Kim, P.Petreczky, A.R. in preparation, 1512.05289 and Phys.Rev. D91 (2015) 054511
[2] Y. Burnier, O.Kaczmarek, A.R. PRL 114 (2015) 082001
[3] Y. Burnier, O.Kaczmarek, A.R. JHEP 1512 (2015) 101
[4] Y. Burnier, O.Kaczmarek, A.R. in preparation
The modification of charmonium and bottomonium production in heavy ion collisions can provide information about the properties of the QGP, including the color screening length. But heavy quarkonia production can be modified by effects that precede QGP formation, as well as by effects that occur after hadronization. This requires that we study quarkonia formation in p+A collisions as well as A+A collisions. If we do so at both RHIC and LHC energies, where the mix of contributing effects is different due to the different initial temperatures, heavy quark production cross sections and kinematic effects, then we greatly improve our prospects for isolating the effects due to the QGP. This strategy has already shown itself to be successful. In this talk I will review quarkonia production results from the RHIC experiments, compare with those from the LHC experiments, and discuss what comes next.
Since the first heavyion collisions which date back to thirty years ago, quarkonium is considered one among the most important probes of the formation of a plasma of quarks and gluons.
Quarkonium production is, in fact, expected to be strongly modified by the creation of a hot medium. On one side, quarkonium yields are suppressed, due to the Debye screening, with respect to those measured in pp interactions scaled by the number of binary collisions. The size of the suppression depends on the energy of the collision and on the strength of the binding energy between the $c$ and $\bar{c}$ or $b$ and $\bar{b}$ quarks. On the other side, for highenergy collisions, an additional quarkonium production mechanism sets in, i.e. the recombination of the quarks during the collision evolution or at the phase boundary. This process might counterbalance the suppression mechanism.
On top of these hotmatter effects, quarkonium production is also affected by mechanims related to the presence of cold nuclear matter. While the first type of effects can be investigated comparing results for several quarkonium states, obtained, in AA interactions, at different collision energies, the coldmatter effects can be addressed by studying the quarkonium behaviour in collisions systems as pA or dA.
In this talk, an overview of the quarkonium results will be presented, discussing the measurements on $J/\psi$, $\psi$(2S) and $\Upsilon$ states at RHIC and at LHC energies, both in pA (dA) and in AA collisions. Particular emphasis will be given to the most recent results from LHC Run2.
Heavy quarks, i.e. charm and beauty, are produced primarily in the initial, hard partonic scatterings in hadronic collisions.
In pp collisions, their production is well described by perturbative QCD due to their large mass.
In heavyion collisions, heavy quarks propagate through and interact with the hot and dense QCD matter.
Therefore, measurements of heavyflavour production provide relevant information on the early stage of the collisions and partonmedium interaction.
A strong suppression of heavyflavour production has been observed at high $p_{\rm{T}}$ with respect to the cross
section measured in pp collisions and scaled by the number of nucleonnucleon collisions.
Such suppression has not observed in pA collisions which is expected absence of QGP.
Thus the suppression in PbPb collisions is a result of final state effects related to the energy loss of heavy quarks.
In addition, a collectivity of heavyflavour productions was found in azimuth in noncentral heavyion collisions.
Those results indicate that heavy quarks strongly interact with the matter created by heavyion collisions.
In the Large Hadron Collider (LHC), open heavyflavour productions in the heavyion collisions (PbPb) has carried by measuring D mesons, leptons from semileptonic decay of heavyflavours and jets which are original from heavy quarks. In this presentation, those results are shown and discussed with theoretical calculations to understand the properties of the QCD matter and heavyflavour productions.
We compute the QGP suppression of $\Upsilon(1s)$, $\Upsilon(2s)$, $\Upsilon(3s)$, $\chi_{b1}$, and $\chi_{b2}$ states in \mbox{$\sqrt{s_{NN}}=2.76$ TeV} PbPb collisions. Using the suppression of each of these states, we estimate the inclusive $R_{AA}$ for the $\Upsilon(1s)$ and $\Upsilon(2s)$ states as a function of $N_{\rm part}$, $y$, and $p_T$ including the effect of excited state feed down. We find that our model provides a reasonable description of preliminary CMS results for the $N_{\rm part}$, $y$, and $p_T$dependence of $R_{AA}$ for both the $\Upsilon(1s)$ and $\Upsilon(2s)$. Comparing to our previous model predictions, we find a flatter rapidity dependence, thereby reducing some of the tension between our model and ALICE forwardrapidity results for $\Upsilon(1s)$ suppression.
Literature:
1) B. Krouppa, R. Ryblewski, M. Strickland, Phys.Rev. C92 (2015) no.6, 061901
2) M. Strickland, Phys.Rev.Lett.107,132301 (2011)
3) M. Strickland, D. Bazow, Nucl.Phys.A879, 25 (2012)
Section E: QCD and New Physics
Physics beyond the Standard Model with hadronic physics precision experimental data and precision calculations.
Conveners: W. Detmold (MIT), M. Gersabeck (U. Manchester), F. J. LlanesEstrada (UC Madrid), E. Mereghetti (Los Alamos NL), J. Portoles (IFIC, Valencia)
The anomalous magnetic moment of the muon $(g2)_\mu$ has been measured and computed to very high precision of about 0.5 ppm. For more than a decade, a discrepancy has persisted between experiment and Standard Model prediction, now of about $3\sigma$. The main uncertainty of the theory prediction is due to strong interaction effects. With the expected improvement of the input for hadronic vacuum polarisation, in a few years the subleading hadronic lightbylight (HLbL) contribution will dominate the theory error.
While some constraints from QCD exist, the calculation of the HLbL contribution to the $(g2)_\mu$ is plagued by a substantial model dependence. In this talk, I will present a dispersive approach to HLbL scattering, based on the fundamental principles of unitarity and analyticity. We have derived a Lorentz decomposition of the HLbL tensor that is fully gaugeinvariant and crossing symmetric. The scalar coefficient functions of this tensor decomposition are free of kinematic singularities and zeros and fulfil Mandelstam's doubledispersive representation. The dispersive formalism defines unambiguously and in a modelindependent way both the pionpole and the pionbox contribution. Twopion rescattering effects are included in a partialwave picture.
Our dispersive formalism shows a path towards a datadriven determination of the HLbL contribution to the $(g2)_\mu$.
The Muon g2 Experiment at Fermilab aims to measure the anomalous magnetic moment of the muon to a precision of 140 parts per billion. This fourfold improvement over the previous Brookhaven E821 measurement provides significant insight into the tantalizing 3.5 standard deviation discrepancy between measurement and the Standard Model prediction
The measurement of the anomalous magnetic moment at the design precision requires measurement of both the spin precession rate and the magnetic field strength, each with a 70 ppb systematic uncertainty, with projected equal statistical and systematic uncertainties of 100 ppb.
This talk will provide an overview and status of the experiment along with the measurement methodology.
The Qweak experiment, which ran for two and a half years at Jefferson Lab,
will precisely determine the weak charge of the proton by measuring the
parityviolating asymmetry in elastic ep scattering at 1.1 GeV using a
longitudinally polarized electron beam and a liquid hydrogen target at a
low momentum transfer of $Q^2 = 0.025 \left(\textrm{GeV/c} \right)^2$. The
weak charge of the proton is predicted by the Standard Model and any
significant deviation would indicate physics beyond the Standard Model.
The technical challenges and experimental apparatus for measuring the weak
charge of the proton will be discussed, as well as the method of
extracting the weak charge of the proton. The results from a small subset
of the data, that has been published, will also be presented. Furthermore
an update will be given of the current status of the data analysis and of
several of ancillary experiments performed.
In the previous decade, the topic of the nucleon's nonperturbative or $\it{intrinsic}$ charm content has enjoyed something of a renaissance, largely motivated by theoretical developments involving quark modelers and PDFfitters. In this talk I will briefly describe the importance of intrinsic charm to various issues in highenergy phenomenology, and survey recent progress in constraining its overall normalization and contribution to the momentum sum rule of the nucleon. I end with the conclusion that progress on the side of calculation has now placed the onus on experiment to unambiguously resolve the proton's intrinsic charm component.
Current experiments aim at measuring parameters of Standard Model to an unprecedented accuracy, and as a consequence require theoretical calculations of radiative corrections that match that precision. The socalled dispersion corrections, or hadronic box corrections represent one of the main limitations of the reach of modern experiments in determining SM parameters and constraining the New Physics contributions in lowenergy experiments. I review the state of the art of the hadronic structuredependent corrections to the measurement of the charge radii of light nuclei (most importantly, the proton radius puzzle) and the running of the weak mixing angle accessed with parityviolating electron scattering and parity nonconservation in atoms.
Experimental measurements of muonic hydrogen bound states have recently started to take place and provide a powerful setting in which to study the properties of QCD. We profit of the power of effective field theories (EFTs) to provide a theoretical setting in which to study muonic hydrogen in a model independent fashion. In particular, we compute expressions for the Lamb shift and the hyperfine splitting.
These expressions include the leading logarithmic ${\mathcal O}(m_{\mu}\alpha^6)$ terms, as well as the leading ${\mathcal O}(m_{\mu}\alpha^5\frac{m_{\mu}^2}{\Lambda_{\text QCD}^2})$ hadronic effects. Most remarkably, our analyses include the determination of the spindependent and spinindependent structure functions of the forward virtualphoton Compton tensor of the proton to ${\mathcal O}(p^3)$, using HBET and including the Delta particle. Using these results we obtain the leading hadronic contributions to the Wilson coefficients of the leptonproton four fermion operators in NRQED. The spinindependent coefficient yields a pure prediction for the twophoton exchange contribution to the muonic hydrogen Lamb shift, which is the main source of uncertainty in our computation. The spindependent coefficient yields the prediction of the hyperfine splitting. The use of EFTs crucially helps us organizing the computation, in such a way that we can clearly address the parametric accuracy of our result. Furthermore, we review in the context of NRQED all the contributions to the energy shift of $\mathcal O(m_r\alpha^5)$, as well as those that scale like $m_r\alpha^6\times$ logarithms.
Minijets and jets are produced in large numbers in nuclear collisions at TeV energies, so that there are many of them in a single fireball. They deposit nonnegligible amount of momentum and energy into the hydrodynamically expanding bulk and cause anisotropies of the expansion. Moreover, due to their multiple production in a single event the resulting anisotropies are correlated with the collision geometry and thus contributes positively also to eventaveraged anisotropies in noncentral collisions. Using simulations with threedimensional ideal hydrodynamic model we demonstrate the importance of this effect. It must be taken into account if conclusions about the properties of the hot matter are to be drawn.
We present novel method for the organisation of events. The method is based on comparing eventbyevent histograms of a chosen quantity $Q$ that is measured for each particle in every event. The events are organised in such a way that those with similar shape of the $Q$histograms endup placed close to each other.
We apply the method on histograms of azimuthal angle of the produced hadrons in ultrarelativsitic nuclear collisions. By selecting events with similar azimuthal shape of their hadron distribution one chooses events which are likely that they underwent similar evolution from the initial state to the freezeout. Such events can more easily be compared to theoretical simulations where all conditions can be controlled. We illustrate the method on data simulated by the AMPT model.
A Large Ion Collider Experiment (ALICE) was designed for the study of the strongly interacting medium created in heavyion collisions at LHC energies, the QuarkGluon Plasma. Heavy quarks (charm and beauty) are very powerful probes to study this state of matter, since they are produced in the early stages of heavyion collisions and they traverse the QCD medium interacting with its constituents. Together with charmed mesons, the measurement of Λc in PbPb collisions would address the baryon over meson enhancement in the heavyquark sector, giving an insight into the hadronization mechanisms. The measurements of the Λc production in pp and pPb collisions provide the necessary baseline to understand the heavyion collision results and to measure the total charm cross section. In this poster we will present the status of the charmed baryon Λc analyses in pp collisions at √s = 7 TeV and pPb collisions at √sNN = 5.02 TeV, via the reconstruction of the decay channels Λc → pKπ and Λc → pK0S. Furthermore, we will discuss the perspectives for future measurements of Λc. In particular, with the ITS upgrade (after the second long LHC shutdown) which will improve the track impact parameter resolution, the tracking efficiency and the pT resolution, the Ʌc could be measured for the first time in PbPb collisions.
Hadron physics
We present a firstprinciples study of anomaly induced transport phenomena by performing real time lattice simulations with dynamical fermions coupled simultaneously to nonAbelian SU(Nc) and Abelian U(1) gauge fields. We investigate the behavior of vector and axial currents
during a sphaleron transition in the presence of an external magnetic field, and demonstrate how the interplay of the Chiral magnetic (CME) and Chiral separation effect (CSE) lead to the formation of a propagating wave. We also analyze the quark mass dependence of these phenomena
and extract spectral information about the carriers of axial and vector charge.
Model parameter free investigations of YangMills theory and quenched QCD in the vacuum are presented as a necessary prerequisitve for corresponding investigations of the QCD phase structure with the functional renormalisation group equation. Preliminary results for YangMills theory at finite temperature are discussed. Finally, a phenomenological application of the vacuum results to the etaprimemeson mass at the chiral crossover is presented.
We calculate the potential between static quarks in the fundamental representation of the F4 exceptional gauge group using domain structures of the thick center vortex model. As nontrivial center elements are absent, the asymptotic string tension is lost while an intermediate linear potential is observed. SU(3) is a subgroup of F4. Investigating the decomposition of the 26 dimensional representation of F4 to the SU(3) representations, might explain what accounts for the intermediate linear potential, in the exceptional groups with no center element.
Electromagnetic processes are known to be a good source of information on the meson inner structure. Analysis of these processes turned out to be particularly fruitful in case of scalar mesons which emerge eg. in the phi(1020) radiative decays in both \pi\pi and \pi\eta channels.
Photoproduction of isoscalar and isovector scalar resonances can be treated as a complementary source of information on the scalar meson
structure. Here we are concerned with the photoproduction of isovector scalars, ie. a_0(980) and a_0(1450). Moreover, we are interested in photoproduction at photon energies of about 10 GeV, ie. energies achievable in new JLab experiments CLAS12 and GlueX. In this kinematic region the process is dominated by the t channel meson exchange which leads to production of pseudoscalar pairs \pi\eta, K\overline{K} and \pi\eta'. These in turn can resonantly interact in the final state. So, construction of the photoproduction amplitudes is inevitably the coupled channel problem.
In ref.[1] we constructed the \pi\etaK\overline{K} coupled channel photoproduction amplitudes where a_0(980) and a_0(1450) resonances emerged due to final
state interactions. Here we present the extended version of the model which takes into account also the \pi\eta' channel. The model is also applicable to higher partial waves (see [2]) and is relevant in the context of CLAS12 and GlueX experiments to be started shortly at Jefferson Laboratory, USA. In these experiments the \pi\eta, K\overline{K} and \pi\eta' pairs will be photoproduced copiously (also by polarized photons) enabling the partial wave analysis. Reliable models of the resonance photoproduction a thus timely and opportune.
Literature:
We report on the coupling of an external $t\bar t$ state to a strongly interacting EWSBS. We exploit perturbation theory in the small $M_t/\sqrt{s}$ quantity, whereas the EWSBS is taken as strongly interacting. We use a modified version of the IAM unitarization procedure to model such a strongly interacting regime. The scattering matrix elements $V_L V_L \to V_L V_L$, $V_L V_L \to hh$, $hh\to hh$, $V_L V_L \to t\bar t$ and $hh \to t\bar t$ are computed at NLO level within the framework of a nonlinear Effective Field Theory and the Equivalence Theorem.
We are interested in $t\bar t$ both as initial and final state. Considering it as final state would allow us to study the possible appearance of resonances in the tt production channel at the LHC. And the initial $t\bar t$ state is a first step to look for resonances starting from two gluon states, via the triangle diagram with quark tops inside. Both cases have direct applications to the LHC phenomenology.
We derive three exact sum rules for the spectral function of the electromagnetic current channel at finite temperature, by using operator product expansion and hydrodynamics, focusing on zero spatial momentum case. We also discuss the possibility to use these sum rules to constrain and improve the functional form of the spectral function assumed in the lattice QCD analysis, and to evaluate the transport efficient at the second order, which does not directly appear in the spectral function, from the lattice QCD data.

Within QCD, the light pseudoscalar mesons assume a twofold role: they may be described as quark–antiquark bound states but also have to be interpreted as the (almost) massless (pseudo) Goldstone bosons of the spontaneously broken chiral symmetries of QCD. The application of suitably adapted inversion techniques enables us to construct exact boundstate solutions to the Bethe–Salpeter equation for massless pseudoscalar mesons, in the form of rigorous (and, under particularly favourable circumstances, even analytic) relationships between the underlying interactions and the resulting Bethe–Salpeter solutions. Needless to say, this procedure is not confined to the Salpeter equation but, with little more effort, may be carried over to more general threedimensional reductions of the Bethe–Salpeter formalism.
We investigate the Hdibaryon (uuddss) in holographic QCD [1, 2].
Holographic QCD is derived from a QCDequivalent Dbrane system
in the superstring theory via the gauge/gravity correspondence.
In holographic QCD, all baryons appear as topological chiral solitons
of NambuGoldstone bosons and (axial) vector mesons [1, 2].
In this framework, the Hdibaryon can be described as an SO(3)type
hedgehog state [3]. In this paper, we present the formalism of
the Hdibaryon in holographic QCD, and investigate its properties.
[1] T. Sakai and S. Sugimoto, Prog. Theor. Phys. 113 (2005) 843; 114 (2005) 1083.
[2] K. Nawa, H. Suganuma and T. Kojo, Phys. Rev. D75 (2007) 086003.
[3] A.P. Balachandran et al., Phys. Rev. Lett. 52 (1984) 887.
The presentation is based on these works
1) Heavy Quark Entropy shift: From the Hadron Resonance Gas to Power Corrections
By E. Megias, E. Ruiz Arriola, L.L. Salcedo.
arXiv:1605.04453 [hepph].
2) Heavy quarkantiquark free energy and thermodynamics of stringhadron avoided crossings
By E. Megias, E. Ruiz Arriola, L.L. Salcedo.
arXiv:1603.04642 [hepph].
3) Heavy ${\bar Q}Q$ free energy from hadronic states
By E. Megías, E. Ruiz Arriola, L.L. Salcedo.
arXiv:1507.08606 [hepph].
10.1016/j.nuclphysbps.2016.02.034.
Nucl.Part.Phys.Proc. 9397 270272, Nucl.Part.Phys.Proc. 270272 (2016) 170174.
4) Quark properties from the Hadron Resonance Gas
By E. Ruiz Arriola, L.L. Salcedo, E. Megias.
arXiv:1505.02922 [hepph].
10.5506/APhysPolBSupp.8.439.
Acta Phys.Polon.Supp. 8 (2015) no.2, 439.
5) Quark Hadron Duality at Finite Temperature
By E. Ruiz Arriola, L.L. Salcedo, E. Megias.
arXiv:1410.3869 [hepph].
10.5506/APhysPolB.45.2407.
Acta Phys.Polon. B45 (2014) no.12, 24072454.
Holographic QCD is based on the AdS/CFT duality and offers new nonperturbative approaches to understand the strongly interacting regime of gauge theories. One of the primary questions in Quantum Chromodynamics is the clarification of the whole phase diagram of matter out of quarks and gluons as a function of temperature, baryon or quark chemical potential, and other external parameters.
We use methods of the bottomup AdS/QCD approach to bring out the phase structure of several holographic models in which transition to a deconfined phase is related to a (first order) HawkingPage phase transition. The impact of phenomenological model parameters on the critical temperature and chemical potential is studied in detail. Comparison of the model predictions with results of experimental investigations, lattice QCD simulations and other methods is also done.
Based on the new fit of hadron yield ratios within the multicomponent hadron resonance gas model we have found several remarkable irregularities at chemical freezeout. In particular, 121 hadron multiplicity ratios measured in the nucleusnucleus collisions at AGS, SPS and RHIC energies were successfully described within the new formulation of HRGM with $\chi^2/dof \simeq 63.978/65 \simeq 0.98$.
A dramatic jump in the center of mass collision energy dependence of pressure, energy density and baryonic charge density in the narrow range between 4.3 and 4.9 GeV is found. These irregularities are also accompanied by a sudden increase of the particle decays at chemical freezeout which is seen at this collision energy range.
We argue that a strong correlation which we observe between the previously found irregularities and an enhancement of strangeness production can serve as the quarkgluon plasma formation signature. Thus, we conclude that a dramatic change in the system properties seen in the narrow collision energy range $\sqrt{s_{NN}} = 4.34.9 $ GeV opens entirely new possibilities for experimental studies of quarkgluon plasma properties at NICA JINR and FAIR GSI accelerators.
The magnetic susceptibility of the QCD vacuum is analyzed in the framework of a nonlocal
SU(3) PolyakovNambuJonaLasinio model. We estimate the values of the u and squark tensor coefficients and magnetic susceptibilities and then we extend the analysis to finite temperature systems, comparing numerical results to those obtained in other theoretical approaches and in lattice QCD calculations.
The ATLAS reconstruction algorithm, in RunII, has been improved and extended compared to the one used in RunI. In this presentation, we will discuss the precise measurement of the muon reconstruction efficiency measured in pp collisions at sqrt(s)= 13 TeV in 2015 and 2016 using samples of J/ψ→μμ and Z→μμ decays. The reconstruction efficiency, transverse momentum resolution and momentum scales measurements in the various regions of the detector and for muon momenta between 6 and hundreds of GeV are presented.
The lateral distribution of an atmospheric shower depends on the characteristics of the high energy interactions and the type of the primary particle. The influence of the primary particle in the secondary development of the shower into the atmosphere, is studied by analyzing the lateral distribution of electron and muon showers having as primary particle, proton, photon or iron nucleus.
This study of the lateral distribution can provide useful conclusions for the mass and energy of the primary particle. This paper compares the data that we get from simulations with CORSIKA program with experimental data and the theoretical NKG function expressing lateral electron and muon distribution. Then we modify the original NKG function to fit better to the simulation data and propose a method for determining the mass of the original particle started the atmospheric shower.
Super QCD Lagrangian and Feynman rules; self energies of quark, gluon, squark and gluino fields; 2pt Green's functions of quark bilinears; lattice perturbation theory.
A recently developed extension of the NambuJonaLasinio model includes all the explicit chiral symmetry breaking interactions which contribute
at the same order in the large 1/Nc counting as the UA(1) ’t Hooft flavor determinant [1]. In addition to the usual 4, 6, 8 fermion vertices this
generalization includes the relevant interaction terms proportional to the current quark masses. It has shown an unprecedented success in the correct
description of the low lying mesonic spectra;
in particular an accurate ordering and magnitude of the splitting of states in the low lying pseudoscalar nonet [2]
can be achieved.
As has been shown [3] a correct thermodynamical behavior can be achieved with careful and thouroughly consistent implementation of the regularization procedure
thus avoiding the pitfalls resulting from the inclusion of arbitrarily high momentum states in unregularized contributions to the thermodynamical potential.
The phase diagram of strongly interacting matter as a function of temperature, chemical potential and magnetic field has been a very active topic of research in
recent times, both from the theoretical and experimental sides, with implications ranging from heavy ion collisions to astrophysics.
Here we will present the latest results obtained with this powerful model extension.
References
[1]
A. A. Osipov, B. Hiller, A. H. Blin, Eur. Phys. J. A 49, 14 (2013);
A. A. Osipov, B. Hiller, A. H. Blin, Phys. Rev. D 88, 054032 (2013).
[2]
A. A. Osipov, B. Hiller, A. H. Blin, J. Moreira, arXiv:1606.01945v1
[3]
J. Moreira, B. Hiller, A.A. Osipov, A.H. Blin, Int.J.Mod.Phys. A27 (2012) 1250060
We study here the interaction of DDbar in the isospin I=1 channel in light of recent theoretical advances that allow us to combine elements of the local hidden gauge approach with heavy quark spin symmetry. We find that the exchange of light qqbar is OkuboZweigIizuka (OZI) suppressed and thus we concentrate on the exchange of heavy vectors and of two pion exchange. The latter is found to be small compared to the exchange of heavy vectors, which then determines the strength of the interaction. A barely DDbar bound state decaying into ηcρ and πJ/ψ is found. At the same time we reanalyze the data of the BESIII experiment on e+e→π±(DDbar)∓, from where a Zc(3885) state was claimed, associated to a peak in the (DDbar)∓ invariant mass distribution close to threshold, and we find the data compatible with a resonance with mass around 3875 MeV and width around 30 MeV. We discuss the possibility that this and the Zc(3900) state found at BESIII, reconfirmed at 3894 MeV at Belle, or 3885 MeV at CLEO, could all be the same state and correspond to the one that we find theoretically.
We analyse the secondclass current decays $\tau^{}\to\pi^{}\eta^{(\prime)}\nu_{\tau}$
in the framework of Chiral Perturbation Theory with Resonances.
Taking into account $\pi^{0}$$\eta$$\eta^{\prime}$ mixing,
the $\pi^{}\eta^{(\prime)}$ vector form factor is extracted, in a modelindependent way,
using existing data on the $\pi^{}\pi^{0}$ one.
For the participant scalar form factor,
we have considered different parameterizations ordered according to their increasing fulfillment of
analyticity and unitarity constraints.
We start with a BreitWigner parameterization dominated by the $a_{0}(980)$ scalar resonance
and after we include its excited state, the $a_{0}(1450)$.
We follow by an elastic dispersion relation representation through the Omn`{e}s integral.
Then, we illustrate a method to derive a closedform expression for the
$\pi^{}\eta$, $\pi^{}\eta^{\prime}$ (and $K^{}K^{0}$) scalar form factors in a coupledchannels treatment.
Finally, predictions for the branching ratios and spectra are discussed emphasizing the error analysis.
An interesting result of this study is that both $\tau^{}\to\pi^{}\eta^{(\prime)}\nu_{\tau}$ decay channels
are promising for the soon discovery of secondclass currents at BelleII.
We also predict the relevant observables for the partner $\eta^{(\prime)}_{\ell 3}$ decays,
which are extremely suppressed in the Standard Model.
Fixed points in QCD can appear when the number of quark flavors ($N_f$) is increased above a certain critical value as proposed by Banks and Zaks (BZ). There is also the possibility that QCD possess an effective charge indicating an infrared frozen coupling constant. In particular, an infrared frozen coupling associated to dynamical gluon mass generation (DGM) does lead to a fixed point even for a small number of quarks. We compare the BZ and DGM mechanisms, their $\beta$ functions and fixed points, and within the approximations of this work, which rely basically on extrapolations of the dynamical gluon masses at large $N_f$, we verify that near the so called QCD conformal window both cases
exhibit fixed points at similar coupling constant values ($g^*$). We argue that the states of minimum vacuum energy, as a function of the coupling constant up to $g^*$ and for several $N_f$ values, are related to the dynamical gluon mass generation mechanism.
Introduction
Chiral model with $\mbox{SU}(4)\times\mbox{U}(1)$ HLS
Relations obtained from the emergent symmetry
Numerical analysis
Summary
Within a relativistic dispersion approach based on the constituentquark model, we extract the strong couplings of three mesons among which there is, at least, one charmonium from the residues of resonance poles in adequate transition form factors for timelike momentum transfer. Confrontation of our results with corresponding earlier ones by QCD sum rules reveals significant disagreement between the outcomes of these two approaches.
We use the local hidden gauge approach in order to study the BBbar and BBbar interactions for isospin I=1. We show that both interactions via one light meson exchange are not allowed by the OkuboZweigIizuka rule and, for that reason, we calculate the contributions due to the exchange of two pions, interacting and noninteracting among themselves, and also due to the heavy vector mesons. Then, to compare all these contributions, we use the potential related to the heavy vector exchange as an effective potential corrected by a factor which takes into account the contribution of the other light meson exchanges. In order to look for poles, this effective potential is used as the kernel of the BetheSalpeter equation. As a result, for the BBbar interaction we find a loosely bound state with mass in the range 10587–10601 MeV, very close to the experimental value of the Zb(10610) reported by the Belle Collaboration. For the BBbar case, we find a cusp at 10650 MeV for all spin J=0,1,2 cases.
We study the physics of the stronglycorrelated gluon
plasma with colorcenter vortices in the lattice SU(2)
simulations.
We observe in the deconfinement phase
how the equation of state, gluon propagators and
transport correlators depend on degrees of freedom of
lattice center vortices in the temporal and spatial
directions.
It is found that the magnetic sector of gluons
is more nonperturbative object than the electric one
still at finite temperature.
A new approach to study the mass spectrum of double heavy baryons containing strange and
charmed quarks is proposed. It is based on the separation of variables in the Schrödinger equation in the prolate spheroidal coordinates. Two nonrelativistic potential models are considered.
In the first model, the interaction potential of the quarks is the sum of the Coulomb and nonspherically symmetrical linear confinement potential. In the second model [1] it is assumed that the quark confinement provided by a spherically symmetric harmonic oscillator potential.
In both models the mass spectrum is calculated, and a comparison with previous results [2, 3] from other models is performed.
This work is supported by the Russian Science Foundation (grant No. 161210176).
References
[1] D.U. Matrasulov, F.C. Khanna, Kh.Yu. Rakhimov and Kh.T. Butanov Spectra of baryons containing two heavy quarks, Eur. Phys. J. A 14, 8186 (2002)
[2] Y. Namekawa et all (PACSCS Collaboration), Charmed baryons at the physical point in 2 +1 flavor lattice QCD, Phys. Rev. D 87, 094512 (2013)
[3] Tetsuya Yoshida, Emiko Hiyama, Atsushi Hosaka, Makoto Oka, Katsunori Sadato, Spectrum of heavy baryons in the quark model, Phys. Rev. D 92, 114029 (2015)
QCDlike theories provide testing grounds for truncations of functional equations at nonzero density, since comparisons with lattice results are possible due to the absence of the sign problem. As a first step towards such a comparison, we determine for various theories the chiral and confinement/deconfinement transitions from the quark propagator DysonSchwinger equation at zero chemical potential by calculating the chiral and dual chiral condensates, respectively.
We investigate the magnetohydrodynamics in the presence of an external magnetic field following the powerlaw decay in proper time and having spatial inhomogeneity characterized by a Gaussian distribution in one of transverse coordinates under the Bjorken expansion. The leadingorder solution is obtained in the weakfield approximation, where both energy density and fluid velocity are modified. It is found that the spatial gradient of the magnetic field results in transverse flow, where the flow direction depends on the decay exponents of the magnetic field. We suggest that such a magneticfieldinduced effect might influence anisotropic flow in heavy ion collisions.

We make simulations of the zeromomentum $SU(2)$ Landau gauge gluon correlator both for periodic and zerofield boundary conditions at varying $\beta$ and $L_t * L_s^3$ lattice sizes.
I review the motivation and evidence for the center vortex confinement mechanism, including the relevance of multiplewinding Wilson loops to the confinement problem, and the recent work of Trewartha, Kamleh, and Leinweber connecting center vortices with instantons and chiral symmetry breaking.
We review lattice calculations of the elementary Greens functions of QCD with a special emphasis on the Landau gauge. These lattice results have been of interest to continuum approaches to QCD over the past 20 years. They are used as reference for DysonSchwinger and functional renormalization group equation calculations as well as for hadronic bound state equations. The lattice provides lowenergy data for propagators and threepoint vertices in Landau gauge at zero and finite temperature even including dynamical fermions. Michael MuellerPreussker's important contributions to this field will be remembered in this talk and put into the perspective of his other research interests. We will also report on new results for the triplegluon and the quarkgluon vertex on which Michael
collaborated with us.
While the crucial role of gauge topology was recognized from 1970’s,
confinement was associated with monopoles and chiral symmetry breaking with instantons.
Recognizing presence of nonzero holonomy, van Baal and others discovered
splitting of the instantons into their constituents — the instantondyons.
Several groups now work out properties of their ensembles, which generate
both the deconfinement and chiral phase transitions. The results of mean field and
numerical simulations are in good agreement with lattice data for QCDlike theories.
Furthermore, introducing variable phases for quark periodicity conditions —
known as flavor holonomies — one can switch quark coupling to different dyons, which dramatically
change both transitions. First lattice studies of
modified — so called $Z_N$symmetric QCD — have also found these effects,
thus confirming the instantondyon mechanism.
Chiral anomaly induces a variety of novel macroscopic quantum phenomena in systems possessing charged chiral fermions, including the Chiral Magnetic Effect (CME). I will review the manifestations of CME in nuclear and condensed matter physics, and present recent results on the link between CME and evolution of magnetic helicity.
Following Plato’s definition of Knowledge as Justified True Belief, Aristotle understood Reality, and our description of Reality, as the emergence of actualobservable events (ενεργεία) from potentialities (δυναμει). This model is still the basis of relating models with observations, as illustrated by the following examples: 1) selecting admissible solutions from differential and difference equations (boundary conditions, asymptotic conditions), in electromagnetism, diffusion, scattering, 2) Theory of Phase Transitions, 3) nonequilibrium transitions of selforganizing complex systems, resulting from bifurcations, 4) The measurement problem in Quantum Theory, 5) Statistical Mechanics, Irreversibility and Chaos, 6) Network Dynamics.
The Aristotelian transition to actuality is conditioned by entelechy, filtering or shaping the actual from the possibilities inherent in our models.
We will review the frequentist methods used in High Energy Physics for deriving limits, establishing a discovery and making a measurement in the presence of Nuisance Parameters. In particular asymptotic methods and the Look Elsewhere Effect will be reviewed.
I will review some recent progress in studying the spectra of mesons using firstprinciples lattice QCD calculations. In particular, I will highlight some new results on resonances, nearthreshold states and related scattering phenomena – this is an area which is very interesting experimentally and theoretically and where we have made significant advances in the last few years. An outlook on future prospects will also be given.
The X, Y and Z resonances observed by BaBar, Belle, BESIII, CDF, CLEOc, CMS, D0 and LHCb Collaborations in the last years provide a challenge to our understanding of QCD. Among them the X(3872), first observed in 2003 by Belle, is the most famous one and the X(5568), observed this year by D0, would be (if confirmed) the most recently acquisition to the list of undoubtedly exotic mesons, since its wave function would consist of four different flavors: u, b, d and s quarks. In this talk I present and discuss some experimental information and theoretical calculations about some of these exotic states. I also discuss the possibility that some of them can be just threshold effects instead of real resonances.
The hadron spectrum above the open charm threshold continues to surprise and challenges our understanding of confined systems of strongly interacting particles. While for the established mesons of the X,Y and Z families we have entered the era of precision measurements, new exotic resonances are still being discovered in the meson sector and lately in the baryon sector as well. This talk will review the status of the spectroscopy of these enigmatic hadrons with hidden charm and discuss recent experimental results from the pentaquark candidates to the evidence for multiflavor states.
I will discuss new results and open challenges in open heavy flavor and
quarkonium production in $p+p$ and $p+$Pb collisions at the LHC.
I will discuss (QCD)techniques and calculations for dark matter production at the LHC, but also briefly review the physics case and the theoretical status of dark matter models.
I review current anomalies seen in the quark flavor sector at LHCb and the B factories. I then discuss a simple and minimal model, which can resolve these anomalies in an elegant way.
When an excess appears in LHC data, we should be comparing the data with entire classes of models, to get an immediate sense of which ones could conceivably be relevant. Often, the new physics is likely to be a relatively narrow schannel resonance. In this case, a simplified model of the resonance can translate an estimated signal cross section into modelindependent bounds on the product of the production and decay branching ratios. This quickly reveals whether a given class of models could possibly produce a signal of the required size at the LHC. This talk will outline a general framework, show how it operates for resonances with different numbers of production and decay modes, and analyzes cases of experimental interest, including resonances decaying to dibosons, diphotons, dileptons, or dijets. If the LHC experiments were to report searches for BSM resonances in the simplified limits variable $\zeta$ defined here, the community could home in more quickly on the models most likely to explain any observed excess.
Section A: Vacuum Structure and Confinement
Mechanisms of quark confinement (vortices, monopoles, calorons...) and the structure of the vacuum in nonAbelian gauge theories. Chiral symmetry breaking, and the Dirac spectrum in the lowmomentum region. Studies of ghost and gluon propagators. Confining strings and flux tubes, their effective actions. Renormalons and power corrections. Interface between perturbative and nonperturbative physics.
Conveners: D. Antonov (Heidelberg), M. Faber (TU Vienna), J. Greensite (San Francisco State U)
Focus Subsection: Emergent gauge fields and chiral fermions
Chiral Fermions and anomalous hydrodynamic effects in condensed matter systems, quantum simulators of QCD, topological phenomena in condensed matter systems.
Conveners: T. Schaefer (NC State U), V. Shevchenko (NRC Kurchatov I.)
The properties of matter at finite baryon densities plays an
important role for the astrophysics of compact stars as well as for heavy
ion collisions or the description of nuclear matter. Because of the
sign problem of the quark determinant, lattice QCD cannot be
simulated by standard Monte Carlo at finite baryon densities.
I describe an alternative attempt to treat
dense QCD with an effective 3d lattice theory, which is
valid for very heavy quarks only, but shows all qualtitative features
of nuclear physics emerging from QCD. In particular, the nuclear
liquid gas transition and an equation of state for baryons can be directly calculated from QCD.
The LLR method was recently proposed for numerical computations of continuous density of states. The density of states approach is particularly useful when dealing with metastabilities and for computing freeenergies. In this talk I will review the method and discuss compact U(1) Lattice Gauge Theory, for which our algorithm has proved to be highly efficient and provided results that significantly improve upon the previous literature.
The method can also be applied to theories at finite density affected by the sign problem, reducing a high dimensional oscillatory integral to a onedimensional one. I will discuss our results for the relativistic Bose gas.
Studies of QCDlike theories without a fermion sign problem at finite density by now have a rather long history already. I will report recent results from twocolor QCD, with two instead of the usual three colors, and $G_2$QCD, with gauge group $G_2$ instead of $SU(3)$. Both have bosonic diquark baryons. The physics of those is believed to be fairly well understood and qualitatively resembles QCD at finite isospin density with pion condensation. There is good guidance from effective field theory predictions and model studies of the BECBCS crossover inside the condensed phase. This allows to test effective lattice theories such as those for heavy quarks derived for QCD from combined strongcoupling and hopping expansions. We observe good evidence that they are indeed able to resolve the characteristic differences between the various theories. In order to understand the generic features of the density at very low temperatures for light quarks in more detail as well, at reasonable costs, we have also simulated these theories in two dimensions and compared our results with the corresponding free lattice fermions to better disentangle lattice artifacts from baryonic bound states and identify manifestations of confinement at finite density.
We extract an effective Polyakov line action from an underlying SU(3) lattice gauge theory with dynamical fermions via the relative weights method. The centersymmetry breaking terms in the effective theory are fit to a form suggested by the hoppingparameter expansion, and the effective action is solved at finite chemical potential by a mean field approach. We show results for a small sample of lattice couplings, lattice actions, and lattice extensions in the time direction. We find in some instances that the longrange couplings in the effective action are very important to the phase structure, and that these couplings are responsible for longlived metastable states in the effective theory. Only one of these states corresponds to the underlying lattice gauge theory.
Section B: Light Quarks
Chiral and soft collinear effective theories; sum rules; lattice; SchwingerDyson equations; masses of light quarks; lightquark loops; phenomenology of lighthadron form factors, spectra and decays; structure functions and generalized parton distributions; exotics and glueballs; experiments.
Conveners: J. Goity (Hampton U.), B. Ketzer (Bonn U.), H. Sazdjian (IPN Orsay), N. G. Stefanis (Ruhr U. Bochum), H. Wittig (JGU Mainz)
We summarize results on the internal structure and properties of the pion and kaon as an illustration of how insights into hadron physics can be obtained from calculations based on the DysonSchwinger equations of QCD. The light pseudoscalar mesons are the best possible case for such considerations as the approach is very wellconstrained by symmetries and there is direct connection to continuum QCD. Emphasis is upon the parton structure as a reflection of QCDmechanisms such as dynamical chiral symmetry breaking and flavor symmetry breaking. The full dependence upon the momentum fraction variable $x$ is available this way, and the results here complement and extend the results for low moments obtained from latticeQCD. Specific topics include distribution amplitudes $\phi(x)$, parton distribution functions $q(x)$, and relationships to the ultraviolet behavior of exclusive elastic and transition form factors of pions and kaons. If time permits, we will discuss a simple model exploration of the spacelike correlator approach for obtaining quasipdfs $\tilde{q}(x, P_z)$ that should approach $q(x)$ as $P_z \to \infty $.
Threeflavor chiral perturbation theory with $t,b,c$ quarks decoupled tests the infrared limit of threeflavor QCD. The standard theory $\chi$PT$_3$ (before being unitarized) assumes that there is no infrared fixed point $\alpha_{\mathrm{IR}}$. If $\alpha_{\mathrm{IR}}$ exists, we get chiralscale perturbation theory $\chi$PT$_\sigma$ about a scaleinvariant theory where the quark condensate is also a scale condensate with nine NambuGoldstone (NG) bosons: a massless $0^{++}$ dilaton $\sigma$ ($f_0(500)$ in the real world) as well as $\pi,K,\eta$. The effective Lagrangian for $\chi$PT$_\sigma$ is the standard one modified by $\sigma$dependent terms and factors required to give the correct scaling dimensions, and can be systematically extended to include higherorder and electroweak corrections. The most important result is a neat explanation of the $\Delta I=1/2$ puzzle for kaon decays; we propose to test it on the lattice via $K\to \pi$ with both on shell.
The precise SIDDHARTA value of the energy shift and width of kaonic hydrogen has awaken a renewed interest for the mesonbaryon interaction in the $S=1$ sector. Our study has been carried out based on a chiral SU(3) Lagrangian up to nexttoleading order (NLO) and implementing unitarization in coupled channels, since the presence of $\Lambda(1405)$ resonance makes not applicable a perturbative treatment of the Chiral Lagrangian in the energy region we are dealing with. The parameters of the model have been fitted to a large set of experimental $K^ p$ scattering data in different twobody channels, to threshold branching ratios, and to the above cited data from SIDDHARTA . In contrast to other groups we take into consideration the $K \Xi$ channels which are very important to obtain more reliable values of the fitting parameters, in particular the NLO coefficients. We have shown in [1,2] that the $K^ p \to K \Xi$ reactions are very sensitive to the NLO terms of the Lagrangian and also to the Born direct and cross diagrams. This fact is due to the null direct contribution of the WeimbergTomozawa (WT) term to the scattering amplitude of these particular reactions.
On the other hand, the $K^ p \to \eta \Lambda$ reaction has associated a pure isospin $0$ ($I=0$) amplitude, and therefore, it constrains the relevance of the role played for each isospin component. In general, a good description in terms of the isospin decomposition is crucial to reproduce properly processes in which a single isospin component is filtered, such as for instance the $K_L^ p \to K^+ \Xi^0$ reaction which could be measured at the proposed secondary $K^0_L$ beam at Jlab and which is a pure $I=1$ process. Another interesting measurement is the $\Lambda_b \to J/\psi K \Xi$ decay which filters I=0, as was studied in [3].
[1] A. Feijoo, V. K. Magas and A. Ramos, Phys. Rev. C 92 015206 (2015).
[2] A. Ramos, A. Feijoo and V. K. Magas, arXiv:1605.03767 [nuclth].
[3] A. Feijoo, V. K. Magas, A. Ramos and E. Oset, Phys. Rev. D 92, 076015 (2015).
Recently, the GWU lattice group has evaluated highprecision phaseshift data for $\pi\pi$ scattering in the $I=1$, $J=1$ channel. Unitary Chiral Perturbation Theory describes these data well around the resonance region and for different pion masses. Moreover, it allows to extrapolate to the physical point and estimate the effect of the missing $K\bar{K}$ channel in the twoflavor lattice calculation. The absence of the strange quark in the lattice data leads to a lower $\rho$ mass, and the analysis with U$\chi$PT shows that the $K\bar{K}$ channel indeed pushes the $\pi\pi$scattering phase shift upward, having a surprisingly large effect on the $\rho$mass. The inelasticity is shown to be compatible with the experimental data. The analysis is then extended to all available twoflavor lattice simulations and similar mass shifts are observed. Chiral extrapolations of $N_f=2+1$ lattice simulations for the $\rho(770)$ are also reported.
Huge magnetic fields (MF) up to eB value of the order of the QCD Lambda square are created
for a short time in peripheral heavy ion collisions at RHIC and LHC.The field about four
orders of magnitude less is anticipated to operate in magnetars.This brought about an
extraordinarly large interest to the behavior of quark systems (mesons and baryons) in strong MF.In a series of papers we developed a relativistic formalism for any composed system in MF and evaluated the mass spectrum and the wave functions of mesons and baryons
( rho, pion, neutron, proton) as a function of the MF strength.To separate the internal degrees of freedom we make use of pseudomomentum which commutes with the Hamiltonian in MF and takes the role of the centerofmass momentum.The quarks Green's functions are taken in the FockFeynmanSchwinger representation.The confinement and color Coulomb interactions are derived using the minimal Wilson loop.The dynamical quark masses are introduced via the Dirac einbein formalism.The endresult is the relativistic Hamiltonian to which the additional hyperfine spinspin interaction is added.As anticipated,the hadron wave function takes the form of an elongated ellipsoid in the MF direction with its size along the MF restricted by the confining string tension.Important to note that for the RHIC and LHC MF values the Landau magnetic radius becomes of the order,or smaller,than the hadron size and therefore the hadron mass problem should be solved at the quark level.For the quark system the question is whether MF induces the "fall to the center" phenomenon (zero mass value).We present negative answer to this question.The hadron mass trajectories vs MF values agree with lattice results in cases the latter are available
Section C: Heavy Quarks
Heavylight mesons, heavy quarkonia, heavy baryons, heavy exotics and related topics: phenomenology of spectra, decays, and production; effective theories for heavy quarks (HQET, NRQCD, pNRQCD, vNRQCD, SCET); sum rules for heavy hadrons; lattice calculations of heavy hadrons; heavyquark masses determination; experiments.
Conveners: G. Bodwin (Argonne NL), P. Pakhlov (ITEP, Moscow), J. Soto (U. Barcelona), A. Vairo (TU Munich)
We compute leadingpower fragmentation corrections to $J/\psi$
photoproduction at DESY HERA, making use of the nonrelativistic QCD
factorization approach. Our calculations include parton production cross
sections through order $\alpha_s^3$, fragmentation functions though
order $\alpha_s^2$, and leading logarithms of the transverse momentum
divided by the charmquark mass to all orders in $\alpha_s$. We find
that the leadingpower fragmentation corrections, beyond those that are
included through nexttoleading order in $\alpha_s$, are small relative
to the fixedorder contributions through nexttoleading order in
$\alpha_s$. Consequently, an important discrepancy remains between the
experimental measurements of the $J/\psi$ photoproduction cross section
and predictions that make use of nonrelativisticQCD longdistance
matrix elements that are extracted from the $J/\psi$ hadroproduction
crosssection and polarization data.
We study higher order relativistic corrections to the electromagnetic production crosssection of a heavy quarkonium and a hard photon in the factorization framework of nonrelativistic QCD (NRQCD). We obtain new matching coefficients and discuss the importance of contributions from color octet operators, that were not considered in the previous studies of this process.
References:
[1] J/Psi pair production at large momenta: Indications for double parton scatterings and large alpha_s^5 contributions. By J.P. Lansberg, H.S. Shao. arXiv:1410.8822 [hepph]. Phys.Lett. B751 (2015) 479.
[2] Production of J/psi+eta(c) vs. J/psi+J/psi at the LHC: Impact of Real alpha_s^5 corrections. By J.P. Lansberg, H.S. Shao. [arXiv:1308.0474 [hepph]]. Phys.Rev.Lett. 111 (2013) 122001.
[3] Doublequarkonium production at a fixedtarget experiment at the LHC (AFTER@LHC). By J.P. Lansberg, H.S. Shao. arXiv:1504.06531 [hepph]. Nucl.Phys. B900 (2015) 273294.
[4] Observation of J/psi pair production in pp collisions at sqrt{s}=7 TeV. By LHCb Collaboration. arXiv:1109.0963 [hepex]. Phys.Lett. B707 (2012) 5259.
[5] Measurement of prompt J/psi pair production in pp collisions at sqrt{s} = 7 TeV. By CMS Collaboration. arXiv:1406.0484 [hepex]. JHEP 1409 (2014) 094.
[6] Observation and studies of double J/psi production at the Tevatron. By D0 Collaboration. arXiv:1406.2380 [hepex]. Phys.Rev. D 90 11 (2014) 111101.
[7] Evidence for simultaneous production of J/psi and Upsilon mesons. By D0 Collaboration. [arXiv:1511.02428 [hepex]]. Phys.Rev.Lett. 116 (2016) 082002.
[8] Nexttoleadingorder QCD corrections to the yields and polarisations of J/Psi and Upsilon directly produced in association with a Z boson at the LHC. By B. Gong, J.P. Lansberg, C. Lorce, J.X. Wang. [arXiv:1210.2430 [hepph]]. JHEP 1303 (2013) 115.
[9] Reassessing the importance of the coloursinglet contributions to direct J/psi + W production at the LHC and the Tevatron. By J.P. Lansberg, C. Lorce. [arXiv:1303.5327 [hepph]]. Phys.Lett. B726 (2013) 218.
[10] Nextto leading order QCD corrections to quarkonium + vector bosons hadroproduction. J.P. Lansberg, H.S. Shao, L.P. Sun (work in progress).
[11] Observation and measurements of the production of prompt and nonprompt J/psi mesons in association with a Z boson in pp collisions at sqrt{s} = 8 TeV with the ATLAS detector. By ATLAS Collaboration. arXiv:1412.6428 [hepex]. Eur.Phys.J. C75 (2015) 5, 229.
[12] Measurement of the production cross section of prompt J/psi mesons in association with a W^+/ boson in pp collisions at sqrt{s} = 7 TeV with the ATLAS detector. By ATLAS Collaboration. arXiv:1401.2831 [hepex]. JHEP 1404 (2014) 172.
In this work, we pint out that there exists an approximate degeneracy among heavylight systems with the same $L$.
This is supported by an experimental fact which can be seen from the observed data. This approximate symmetry explains why the GI model obtains results similar to those of the heavylight systems which are fitted well with experimental data. This is because the GI model has this symmetry from the beginning which is broken by the spinorbit interactions. Numerical results of the GI model together with those of other models respecting heavy quark symmetry are compared with the experimental data of the $D$ mesons and they well give similar results to each other.
We analytically show that expectation values of $[H_0,\vec L^{~2}]$ give us at most of the order of $1/m_Q$ for $0^$ and $1^$ states and the similar arguments will give us the same conclustion for other higher states in our model which respects heavy quark symmetry. Note that this order of magnitude, $1/m_Q$, is the same as those which break degeneracy of a spin doublet of heavylight systems. It is shown that there is a rotational symmetry in the limit of $m_Q\to \infty$ and nonrelativistic limit of heavyquark symmetry.
Simple application of our idea to other states can be given by baryons $QQq$ like $\Xi_{cc}^+$, multiquark states in which one light quark is included like $QQ\bar Qq$, and probably other states in which a couple of light quarks can be regarded as a brown mock. A good expample is given by a spectrum of $\Lambda_c$ which gives us $\Lambda_c(2286)$ with $L=0$, $\Lambda_c^+(2595)$ and $\Lambda_c^+(2625)$ with $L=1$, and $\Lambda_c^+(2880)$ and $\Lambda_c^+(2940)$ with $L=2$, where a spin multiplet is given by member/members with the same $L$. $L$ is defined by an angular momentum between a heavy quark $c$ and two light quarks $(ud)$. One can easily see that gaps between different spin multiplets are nearly equal to $\Lambda_{QCD}\sim 300$ MeV, which coincides with the observation of heavylight mesons.
This property may be explainged by adopting a string picture of a heavylight system, i.e., having a fixed end and a free end and connecting both ends with a string.
We determine the $1/m$ and $1/m^2$ spinindependent heavy quarkonium potentials in the unequal mass case with $\mathcal O (\alpha^3)$ and $\mathcal O (\alpha^2)$ accuracy, respectively. Furthermore, we discuss in detail different methods to obtain the potential and we provide the explicit field redefinition that relates them, thus clarifying the relation between different previous partial results.
Of special relevance is the computation of the manifestly gauge invariant $1/m$ and $1/m^2$ potentials in terms of Wilson loops with nexttoleading order (NLO) precision. As an application of our results we derive the theoretical expression for the Bc spectrum in the weakcoupling limit up to nexttonexttonexttoleading order (N$^3$LO).
Our formalism is based on the Covariant Spectator Theory (CST), a framework based on field theory originally developed to study systems of few nucleons. The distinctive feature of this approach is that it approximates the full BetheSalpeterequation by taking into account, effectively, the contributions of both ladder and crossed ladder diagrams in the kernel.
Another notable feature of the CST equations is that they are established in physical Minkowski space. Therefore, the results obtained are not restricted to bound state masses and momentum regions which are free of propagator singularities. This is advantageous over Euclidean formulations (although it entails the difficulty of handling those singularities numerically) because form factors can be computed directly in the timelike region with no need for analytical continuations.
To model phenomenologically the interquark interaction, we adopt a kernel compatible with the requirements of chiral symmetry that contains a linear confining term, a color Coulomb term and a constant. This choice allow us to have a straightforward correspondence with the Cornell potential (plus a constant) and recover, in the nonrelativistic limit, the results from the Schrödinger equation. The parameters that characterize this model, namely the constituent quark masses and coupling constants, are fitted to data and compared with their counterparts provided by other approaches such as lattice QCD and formulations based on the DysonSchwinger equations.
Section D: Deconfinement
QCD at finite temperature; quarkgluon plasma detection and characteristics; jet quenching; transportation coefficients; lattice QCD and phases of quark matter; QCD vacuum and strong fields; heavyion experiments.
Conveners: C. Allton (Swansea U.), E. Iancu (CEA/DSM/Saclay), M. Janik (WUT), P. Petreczky (BNL), A. Vuorinen (U. Helsinki), Y. Foka (GSI)
Motivated by the striking modifications of jets observed both at RHIC and the LHC, significant progress towards the understanding of jet dynamics within QGP has occurred over the last few years. In this talk, I review the recent theoretical developments in the study of mediuminduced jet evolution and energy loss within a perturbative framework. The main mechanisms of energy loss and broadening will be firstly addressed with focus on leading particle calculations beyond the eikonal approximation. Then, I will provide an overview of the modifications of the interference pattern between the different parton emitters that build up the parton shower when propagating through an extended coloured medium. I will show that the interplay between color coherence/decoherence that arises from such effects is the main mechanism for the modification of the jet core angular structure. Finally, I discuss the possibility of a probabilistic picture of the parton shower evolution in the limit of a very dense or infinite medium.
We discuss the evolution of an energetic jet which propagates through a dense quarkgluon plasma
and radiates gluons due to its interactions with the medium. Within perturbative QCD, this
evolution can be described as a stochastic branching process, that we have managed to solve exactly.
We present exact, analytic, results for the gluon spectrum (the average gluon distribution)
and for the higher npoint functions, which describe correlations and fluctuations.
Using these results, we construct the eventbyevent picture of the gluon distribution produced
via mediuminduced gluon branching. In contrast to what happens in a usual QCD cascade
in vacuum, the mediuminduced branchings are quasidemocratic, with offspring gluons
carrying sizable fractions of the energy of their parent parton. We find large fluctuations in the energy loss and in the multiplicity of soft gluons.
The multiplicity distribution is predicted to exhibit KNO (KobaNielsenOlesen) scaling.
These predictions can be tested in Pb+Pb collisions at the LHC, via eventbyevent
measurements of the dijet asymmetry.
Based on ePrint: arXiv:1601.03629 [hepph] published in JHEP 1605 (2016) 008 and work in progress.
The research programme of the ALICE experiment at the LHC focuses on studies of the QuarkGluon Plasma, a state of matter where quarks and gluons are deconfined. The measurement of jets originating from the fragmentation of hardscattered partons in the early phases of a nuclear collision allows one to study parton energy loss in the hot and dense medium. The dependence of the energy loss on the inmedium path length provides deeper insight into the energy loss mechanisms and can be studied by measuring jet production relative to the event plane orientation. Measurements of the jet structure explore possible modifications of the parton fragmentation due to the interaction with the medium.
In this talk, we show results of measurements of charged jet production in central and peripheral \sqrt{s_{NN}} = 2.76 TeV PbPb collisions with respect to the event plane. Furthermore, measurements of a set of jet shapes characterising the longitudinal and transverse jet structure will be discussed. The results are compared with a variety of jet quenching Monte Carlo models.
Longrange multiplicity correlations in intervals separated in pseudorapidity and azimuth are studied in the framework of string fusion approach.
We applied a Monte Carlo model [1,2], in which the string configurations in the transverse plane and rapidity are simulating eventbyevent.
We assumed that the azimuthal anisotropy of particle production is caused by parton energy loss travelling trough the media formed by clusters of fused strings [35]:
$\Delta p_t/\Delta x =  \alpha ( p_t \sqrt { \eta } )^{2/3} $,
where $ \eta $ is a string density.
An additional source of the anisotropy is related to the strong resonances decays.
This approach provides nonzero values of elliptic and higher flows in PbPb and pPb collisions at LHC energies. The obtained results are compared with experimental data.
The author acknowledges SaintPetersburg State University for the research grant 11.38.197.2014.
[1] V. N. Kovalenko, Phys. Atom. Nucl. 76, 1189 (2013), arXiv:1211.6209 [hepph].
[2] V. Kovalenko, V. Vechernin, PoS (Baldin ISHEPP XXI) 077, arXiv:1212.2590 [nuclth], 2012.
[3] M. A. Braun, C. Pajares, Eur. Phys. J. C 71, 1558 (2011).
[4] M. A. Braun, C. Pajares, V. V. Vechernin, Nucl. Phys. A 906, 14 (2013).
[5] M. A. Braun, C. Pajares, V. V. Vechernin, Eur. Phys. J A 51, 44 (2015).
We use holography to analyze the evolution of an ensemble of jets, with an initial probability distribution for their energy and opening angle as in protonproton (pp) collisions, as they propagate through an expanding cooling droplet of strongly coupled plasma as in heavy ion collisions. We identify two competing effects: (i) each individual jet widens as it propagates; (ii) the opening angle distribution for jets within any specified range of energies is pushed toward smaller angles, comparing final jets to initial jets with the same energies. The second effect arises because small angle jets suffer less energy loss and because jets with a higher initial energy are less probable in the ensemble. We illustrate both effects in a simple twoparameter model, and find that their consequence in sum is that the opening angle distribution for jets in any range of energies narrows. We find that either effect can dominate in the mean opening angle for not unreasonable values of the parameters. So, the mean opening angle for jets with a given energy can easily shift toward smaller angles, as experimental data may indicate, even while every jet in the ensemble broadens.
contains fewer narrow and wide jets. Either effect can dominate in the mean opening angle, for not unreasonable values of the parameters. So, the mean opening angle for jets with a given energy can easily shift toward smaller angles, as experimental data may indicate, even while every jet in the ensemble broadens.
Section E: QCD and New Physics
Physics beyond the Standard Model with hadronic physics precision experimental data and precision calculations.
Conveners: W. Detmold (MIT), M. Gersabeck (U. Manchester), F. J. LlanesEstrada (UC Madrid), E. Mereghetti (Los Alamos NL), J. Portoles (IFIC, Valencia)
Permanent Electric Dipole Moments (EDM) of hadrons and leptons provide a unique probe for physics beyond the Standard Model (SM). As EDMs violate P and T symmetries, they also provide information about the matterantimatter asymmetry in the universe. Although the SM prediction for EDMs is beyond the reach of current experiments, the experiments set stringent limits on many beyond SM models. In this talk I will present an overview of selected experimental efforts and discuss their roles towards an improved understanding of the underlying physics. A focus will be the neutron EDM search at TU Munich, which is the first already built apparatus in this field, which plans to reach a more than 10fold improvement. The apparatus is being moved to a new source of ultracold neutrons at ILL within the next year and deals with various novelties to improve the understanding of systematic effects, including the smallest magnetic fields on earth and the investigation of nongaussian statistics in spin precession.
I will provide an overview of various leading contributions to neutron electric dipole moment (EDm) from both the standard model and beyond the standard model and then summarize the status of lattice QCD calculations of the matrix elements of two of the leading novel CP violating interactions  the quark EDM and the quark chromo EDM.
Permanent electric dipole moments (EDMs) are sensitive probes of CP violation beyond the Standard Model. EDM experiments typically involve complicated systems such as hadrons, nuclei, and atoms. I will discuss an effective field theory framework in which EDM measurements can be interpreted in terms of more fundamental concepts. As an example, I illustrate how EDM measurements set strong constraints on CP violation in the Higgs sector. I argue that hadronic and nuclear uncertainties limit the power of EDM searches and discuss strategies that can improve this situation in order get the most out of the rich experimental program.
We will give an overview about the current state of the calculation of diboson
production. For precision measurements at the LHC both NNLO QCD and NLO EW
corrections are important. The Diboson production processes give access to
triple gauge couplings and possible modifications in the form of anomalous
couplings (AC). We will present a study on WZ production with AC at approximate
NNLO QCD using the LoopSim method in combination with the Monte Carlo program
VBFNLO. Higher order corrections to WZ production are dominated by additional
hard jet radiation. We will discuss the use of a dynamical veto based on ratios
of transverse energies to suppress those without introducing problematic logs
like a fixed $p_T$ jet veto.
A collaborative effort to determine the $\Lambda$parameter in 3flavour
QCD by the ALPHA collaboration has just been finalized. This requires the precise
connection of vastly different energy scales, which is achieved using suitable
running couplings in finite volume renormalization schemes and recursive stepscaling methods.
In this talk I focus on the scale evolution from an intermediate scale, $1/L_0$, of
about 4 GeV to scales of O(100) GeV. We use a 1parameter family
of Schroedinger Functional (SF) couplings which are also very
wellsuited for perturbation theory. In particular, their $\Lambda$parameters
can be related exactly and
their respective $\beta$functions are known to 3loop order.
Our precise continuum extrapolated lattice data allows
for stringent tests of renormalized perturbation theory in the high energy regime.
and leads to a determination of the $\Lambda$parameter (in units of $L_0$) with
a total error below 3 percent. To quote such a small error with confidence,
nonperturbative data is required around $\alpha_s = 0.1$.
In particular, our study suggests that the apparent precision
reached with data around $\alpha_s = 0.2$ can be misleading.
(cf. talk by M. Dalla Brida for the determination of $L_0$ in physical units)
In this talk we present the ALPHAcollaboration computation of the threeflavour QCD $\Lambda$parameter. Starting from the value of $\Lambda$ in units of an intermediate energy scale $\mu=1/L_0 \sim 4\, {\rm GeV}$ (cf. talk by S. Sint), we first discuss the connection of this scale and a given hadronic scale, $1/L_{\rm had}$, of a few hundred MeV. The latter is obtained very precisely by determining the nonperturbative scaleevolution of the recently proposed gradient flow coupling between these scales. In a second step, $1/L_{\rm had}$ is expressed in terms of some measurable hadronic quantity using results from the CLScollaboration effort. This allows the $\Lambda$parameter to be determined in physical units.
ALICE (A Large Ion Collider Experiment) is studying the physics of strongly interacting matter, and in particular the properties of the QuarkGluon Plasma (QGP), using protonproton, protonnucleus and nucleusnucleus collisions at the CERN LHC (Large Hadron Collider). The ALICE Collaboration is preparing a major upgrade of the experimental apparatus, planned for installation in the second long LHC shutdown in the years 20192020. A key element of the ALICE upgrade is the construction of a new, ultralight, highresolution Inner Tracking System (ITS). With respect to the current detector, the new ITS will significantly enhance the determination of the distance of closest approach to the primary vertex, the tracking efficiency at low transverse momenta, and the readout rate capabilities. This will be obtained by seven concentric detector layers based on a Si (50 $\mu m$ thick) CMOS pixel sensor with a pixel size of about 30x30 mu$^2$. A key feature of the new ITS, which is optimized for high tracking accuracy at low transverse momenta, is the very low mass of the three innermost layers, which feature a material thickness of 0.3% X0 per layer. This contribution presents the design goals and layout of the new ALICE ITS, with focus on the technical implementation of the main detector components, and the projected detector and physics performance.
ALICE is the only LHC experiment specifically devoted to the study of ultrarelativistic heavy ion collisions. Its main goal is to identify and study a new state of matter, le Quark Gluon Plasma (QGP), where quarks and gluons are deconfined, which might have existed during the first instants of the Universe. One of the most powerful signatures for QGP study is the suppression, within this hot and deconfined medium, of heavy resonances as J/psi et Upsilon. These resonances are measured in ALICE by their dimuon decay thanks to a forward spectrometer.
The muon spectrometer performances are constrained by the presence of a thick absorber, meant to stop most of the hadrons (essentially pions and kaons) before their muonic decay, thus reducing the large noise generated by their decay products. However, the presence of this absorber limits the precision of the measurement of interesting muon properties because of energy loss and multiscattering effects. This implies some limitations on the broadness of the physics results that are actually accessible. For example, only the inclusive production of J/psi can be studied and there is no room to distinguish the J/psi coming from the decay of B mesons. In order to improve the present performances of the dimuon spectrometer and thus enlarge the set of observables that ALICE can measure, a major upgrade project, called Muon Forward Tracker (MFT), is under development. The MFT will consist in a telescope of siliconpixel detectors placed in front of the absorber, which will allow precise backtracking and vertexing from the present spectrometer. This will largely improve the energy resolution in reconstructing the heavy resonances.
The MFT is based on CMOS technology silicon pixels, assembled in Hybrid Integrated Circuits (HIC) that will equip 5 concentric disks around the beam pipe. The main detection element of these circuits is the ALPIDE chip, developed in collaboration with the ALICEITS detector. The chip qualification and performance studies are in their final phase before proceeding to the full production of the finalized chip. In parallel, a study and characterization campaign of the HIC, consisting of several chips connected to the final readout system developed for the MFT, is presently ongoing. This fundamental step of the project will lead to the full qualification of the base element of the MFT detector, allowing the start of the production of some 500 circuits that will equip the MFT.
In this talk, we will present the physics goal of the MFT detector and a detailed status of the R&D activities that will lead to the construction of this new detector, fundamental for the upgrade of the muon program within the ALICE collaboration.
The muon g2/EDM proposed experiment at JPARC is a promising and innovative attempt at the field of Precision Physics. The sensitivity goal of 0.1ppm will test the limits of our current understanding, and may probe for BSM observations.
Our project seeks out to investigate the computational techniques required by the experimental process.
The GEANT4 framework was used to simulate the late detection phase. This allowed us to observe the event hierarchy in different energies, and construct an eventselection algorithm.
Using techniques pertaining to Machine Learning and Image Feature Extraction, we were able to describe a Pattern Recognition algorithm, along a generic representation of these event categories
Finally, the modular GenFit2 framework was used to reconstruct tracks from sparse digitized event data.
In high energy physics experiments a CsI photocathode coupled to a gaseous detector is used in most of the RICH detectors to identify charged hadrons. These RICH detectors have shown to be efficient and stable over long periods of time. A review of the important RICH detectors used around the world, and the technology behind them, will be shown.
The main goal of the CBM experiment at FAIR is to study the behaviour of nuclear matter at very high baryonic density in which the transition to a deconfined and chirally restored phase is expected to happen. The promissing signatures of this new state are the enhanced production of multistrange particles, production of hypernuclei and dibaryons. Theoretical models predict that single and double hypernuclei, and heavy multistrange shortlived objects are produced via coalescence in heavyion collisions with the maximum yield in the region of SIS100 energies. The discovery and investigation of new hypernuclei and of hypermatter will shed light on the hyperonnucleon and hyperonhyperon interactions. The key CBM observables include particles containing hidden charm, open charm and lowmass vector mesons decaying into leptons. Particularly demanding is the measurement of open charm particles with very low multiplicities, which is based on the real time selection of displaced vertices with an accuracy of about 50 μm. Results of feasibility studies of the key CBM oservables in the CBM experiment are discussed.
Machine learning techniques; data fitting and extraction of signals; new developments in unfolding methods; averaging and combination of results
Conveners: T. Dorigo (INFN, Italy)
The most accurate method to combine measurement is to build a combined likelihood function and use it to perform the desired inference. This is not always possible for various possible reasons, hence approximate methods are often convenient. Among those, the best linear unbiased estimator (BLUE) is the most popular, allowing to take into account individual uncertainties and their correlations. The method is unbiased by construction if the true uncertainties and their correlations are known, but it may exhibit a bias if uncertainty estimates are used in place of the true ones, in particular if those estimated uncertainties depend on measured values. In those cases, an iterative application of the BLUE method may reduce the bias of the combined measurement.
Often physicists need to calculate the confidence interval for the ratio of two measurements and many times just use the socalled “error propagation” of the corresponding uncertainties, without being aware of the approximations involved and the limitations of this approach. We will explore these limitations, as well as some alternative and more accurate methods. “Exact” methods for the case of ratio of two quantities following a Poisson law will be described, together with approximations to more general cases showing good coverage properties.
Based on
Estimating the significance of a signal in a multidimensional search
Ofer Vitells, Eilam Gross (Weizmann Inst.). May 2011. 5 pp.
Published in Astropart.Phys. 35 (2011) 230234
A method is presented for the reduction of large sets of related uncertainty sources into strongly reduced representations which retain a suitable level of correlation information for use in many cases. The method provides a selfconsistent means of determining whether a given analysis is sensitive to the loss of correlation information arising from the reduction procedure. The method is applied to the ATLAS Jet Energy Scale (JES) uncertainty, demonstrating that the set of 60+ independent sources can be reduced to form a representation constructed of 3 nuisance parameters. By forming a set of four such representations, it is shown that JES correlation information is retained or probed over the full parameter space to within an average of 1%. This procedure is expected to significantly reduce the computational requirements placed upon early ATLAS searches in the upcoming 2015 dataset while still providing sufficient performance and correlation structure to avoid changing the analysis results.
The Large Hadron electron Collider (LHeC) is a proposed facility which will exploit the new world of energy and intensity oered by the LHC through collisions with a new 60 GeV electron beam. Designed for synchronous operation with the other LHC experiments, the LHeC will be a high luminosity ep and eA collider with a wide ranging physics program on high precision deep inelastic scattering and new physics. Electron proton scattering is also considered as an option for of the Future Circular Collider (FCChe). Highlights from the $ep$ and $eA$ physics program will be illustrated along with details on the status of the activities from accelerator, and detector design and a possible roadmap.
Report at the Session: Future Perspectives, Upgrades, Instrumentation
Vertex detector for open charm measurements with NA61/SHINE at SPS at CERN
G.A.Feofilov $^1$$^†$ (for NA61/SHINE Collaboration)
(1) SaintPetersburg State University
$^†$ Email: feofilov@hiex.phys.spbu.ru
Search for the critical point of strongly interacting matter and studies of the onset of deconfinement are in the focus of the current NA61/SHINE experimental programme. The last one is being conducted by means of investigation of fluctuations and system size dependences of various observables in hadron collisions energy scan at the SPS at CERN. Quite new and enhanced physics capabilities are opening after completion of the ongoing modernization of the NA61 / SHINE installation, when the total rate of statistics will be increased more than 10 times, thus allowing the study of open charm in PbPb collisions at the SPS energies. It is expected that studies of rare processes of heavy flavors production (first of all, of particles containing charm quarks) and their interaction with the medium produced in such collisions  will allow us to get new information about the physical processes in the area of the hypothethical critical point of nuclear matter. These studies could help also to discriminate existing theoretical models relevant to the initial stages of hadron collisions, evolution of quarkgluon plasma, matter induced changes in the yields of quarkonia, energy loss mechanisms, …etc.
In this report we present a physics motivation followed by the brief status of the ongoing development of the dedicated Vertex Detector (VD) designed for open charm measurements in PbPb collisions with the NA61/SHINE at CERN SPS. The task is quite challenging in view of very low yields at the threshold region of open charm production. It is being solved for the NA61/SHINE by the application of the coordinate sensitive Sisensor chips in CMOS technology for the high precision tracking to the to the vertices of hadronic decays. This precise tracking is done by a set of four Sisensor planes in combination with the particle identification by the NA61/SHINE TPSs. The extremely low material budget of the VD (below 0.3 % X/Xo for each tracking plane) is achieved by the implementation of proven ALICE technologies of the extralightweight thermo and mechanically stable structures for Sidetectors cooling and support. After completion of the VD, due to its high spatial tracking resolution and low multiple scattering contributin, it will be possible to apply geometrical selections and to separate the Dmesons decay vertex from the interaction one.
The author of this report acknowledges the support by the Russian Science Foundation research grant 161210176.
The Micro Vertex Detector (MVD) will consist of four planar detector stations located at 5cm to 20cm downstream the target.
Its design is driven by the challenge to identify the decay vertices of particles carrying opencharm, which calls for a high spatial resolution ($\sim 5\mu m$) and a very light material budget of $0.3\%\ (0.5\%)\ X_0$ for the first (following) stations.
To match these requirements, we will employ $50~\mu m$ thin CMOS Monolithic Active Pixel Sensors, which will be provided by the IPHC Strasbourg.
The heat dissipated by the sensors is evacuated via support structures relying on highly heatconductive carbon materials (CVD diamond, TPG), which is essential for vacuum operation.
Dedicated flex print cables are used to power the sensors and to transport the data corresponding to up to $\sim 7 \times 10^5 hits/mm^2/s$ (peak) towards the DAQ system.
We introduce our concept for the MVD and discuss technological challenges related to its mechanical integration.
Moreover, we show the results of a feasability study, which was carried out with a prototype (PRESTO) realizing a full quadrant of a detector station.
Modern and future heavyion experiments are focused on measurements of very rare particles at interaction rates up to 10 MHz with data flow of up to 1 TB/s, that cannot be fully stored on currently available storage devices. The data flow should be reduced by selecting collisions with potentially interesting physics. Therefore, full reconstruction of the collision topology including reconstruction of shortlived particles is required already in real time with the experiment. The algorithms for online reconstruction should be fast, vectorized, parallelized, and portable in order to utilize the full potential of different manycore CPU/GPU computer architectures.
One of the most promising approaches to the search of particle trajectories (tracks) in the detector system is the Cellular Automaton (CA) track finder. The algorithm is based on consistent accumulation of the tracking information by building of short track segments, linking them according to the track model and selecting the best track candidates.
After tracks are found, they parameters are properly estimated within the Kalman Filter (KF) approach.
Next, shortlived particles are reconstructed covering signals from all physics cases: strange particles, strange resonances, hypernuclei, low mass vector mesons, charmonium, and opencharm particles.
All discussed algorithms are fully vectorized and parallelized and show a strong linear scalability on manycore architectures.
One of the most challenging questions in contemporary physics is why and how quarks are confined into hadrons. The electromagnetic structure of hadrons, parameterised in terms of electromagnetic form factors, EMFF's, can provide a key.
The focus of this talk is baryon EMFF's. EMFF's have been a powerful tool in understanding the structure of nucleons for more than 60 years but the new techniques and larger samples available at modern facilities have given rise to a renewed interest for the field. Recently, the access to hyperon structure by hyperon timelike EMFF provides an additional dimension.
The BEijing Spectrometer (BES III) at the Beijing Electron Positron Collider (BEPCII) in China is the only running experiment where timelike baryon EMFF's can be studied in $e^+e^ \rightarrow B\overline{B}$. The BES III detector is an excellent tool for baryon form factor measurements thanks to its near 4$\pi$ coverage, precise tracking, PID and calorimetry. All hyperons in the SU(3) spin ½ octet and spin 3/2 decuplet are energetically accessible within the BEPCII energy range.
Recent data on proton and $\Lambda$ hyperon form factors will be presented. Furthermore, a worldleading data sample was collected in 20142015 for precision measurements of baryon form factors. In particular, the large data sample will enable a measurement of the relative phase between the electric and the magnetic form factors for $\Lambda$ hyperons. The modulus of the phase can be extracted from the $\Lambda$ polarisation, which in turn is experimentally accessible via the weak, parity violating $\Lambda \rightarrow p \pi^$ decay. Furthermore, from the spin correlation between the outgoing $\Lambda$ and $\overline{\Lambda}$, the sign of the phase can be extracted. The methods will be outlined and the prospects of the BES III form factor measurements will be given. In particular, I will discuss how future hyperon EMFF measurements will benefit from a planned upgrade of the BES III detector.
In the ever increasing pileup of the Large Hadron Collider environment the trigger systems of the experiments have to be exceedingly sophisticated and fast at the same time in order to increase the rate of relevant physics processes with respect to background processes.
The Fast TracKer (FTK) is a track finding implementation at hardware level that is designed to deliver fullscan tracks with $p_{T}$ above 1 GeV to the ATLAS trigger system for every L1 accept (at a maximum rate of 100kHz). To accomplish this, FTK is a highly parallel system which is currently under installation in ATLAS. It will first provide the trigger system with tracks in the central region of the ATLAS detector, and next year it is expected that it will cover the whole detector.
The system is based on pattern matching between hits coming from the silicon trackers of the ATLAS detector and 1 billion simulated patterns stored in specially designed ASIC chips (Associative memory – AM06). In a first stage, coarse resolution hits are matched against the patterns and the accepted hits undergo track fitting implemented at FPGA level. Tracks above the 1GeV threshold are delivered to the High Level Trigger within about 100 μs. The resolution of the tracks coming from FTK is close to the offline tracking resolution and it will allow for reliable detection of primary and secondary vertices at trigger level and improved trigger performance for bjets and tau leptons.
This presentation will provide an overview of the FTK system architecture and its commissioning status. Moreover, its expected performance will be briefly presented.
Machine learning techniques; data fitting and extraction of signals; new developments in unfolding methods; averaging and combination of results
Conveners: T. Dorigo (INFN, Italy)
I begin with an introduction to deep learning methods and the kinds of problems in particle physics to which the methods could be usefully applied, such as searching data for evidence of new physics. Then I discuss the Bayesian connection. I conclude with a perspective on what data analysis might look like in the not too distant future.
Statistical classification models are commonly used to separate a signal from a background. In this talk we face the problem of isolating the signal of the double Higgs production using the decay channel in which each boson decays into a pair of bquarks. Typically in this context non parametric methods are used, such as Random Forest or different types of Boosting. We remain in the same non parametric framework, but we propose to face the problem following a Bayesian approach. A Dirichlet process is used as prior for the random effects in a logit model which is fitted by leveraging the PolyaGamma data augmentation algorithm. Refinements of the model include the insertion in the simple model of Psplines to relate explanatory variables with the response and the use of Bayesian trees (BART) to describe the atoms in the Dirichlet process.
The problem of correcting data for detector effects (unfolding) is
disussed, with emphasis on practical difficulties showing up
in particle physics. A selection of unfolding methods
commonly used in particle physics is presented, such as
iterative algorithms (D'Agostini), methods based on matrix
decomposition (SVD unfolding) and fits with Tikhonov regularisation
(TUnfold). The differences between the methods are discussed and their
weak and strong points are compared.
In ATLAS, several unfolding methods are used to correct experimental measurements for detector effects, like acceptance and resolution. These methods use as input the raw experimental distributions, as well as Monte Carlo simulation for the description of the detector effects. The systematic uncertainties associated to the various unfolding methods are evaluated. The statistical and systematic uncertainties affecting the raw measurements and/or the simulation are propagated through the unfolding procedure. The resulting corrected measurements with their uncertainties can be directly compared with the corresponding theoretical predictions.
Centrality, as a geometrical property of the collision, is crucial for the physical interpretation of nucleusnucleus and protonnucleus experimental data. However, it cannot be directly accessed in eventbyevent data analysis. Contemporary methods of the centrality estimation in AA and pA collisions usually rely on a single detector (either on the signal in zerodegree calorimeters or on the multiplicity in some semicentral rapidity range). In the present work, we made an attempt to develop an approach for centrality determination that is based on machinelearning techniques and utilizes information from several detector subsystems simultaneously. Different event classifiers are suggested and evaluated for their selectivity power in terms of the number of nucleonsparticipants and the impact parameter of the collision. Finer centrality resolution may allow to reduce impact from socalled volume fluctuations on physical observables being studied in heavyion experiments like ALICE at the LHC and fixed target experiment NA61/SHINE on SPS.
This work is supported by the Russian Science Foundation, GRANT 161210176.
Section A: Vacuum Structure and Confinement
Mechanisms of quark confinement (vortices, monopoles, calorons...) and the structure of the vacuum in nonAbelian gauge theories. Chiral symmetry breaking, and the Dirac spectrum in the lowmomentum region. Studies of ghost and gluon propagators. Confining strings and flux tubes, their effective actions. Renormalons and power corrections. Interface between perturbative and nonperturbative physics.
Conveners: D. Antonov (Heidelberg), M. Faber (TU Vienna), J. Greensite (San Francisco State U)
Focus Subsection: Emergent gauge fields and chiral fermions
Chiral Fermions and anomalous hydrodynamic effects in condensed matter systems, quantum simulators of QCD, topological phenomena in condensed matter systems.
Conveners: T. Schaefer (NC State U), V. Shevchenko (NRC Kurchatov I.)
We extend the covariant variational approach for YangMills theory
in Landau gauge to nonzero temperatures. The renormalization of the system
is revisited and it is shown how the zerotemperature counter terms can be
used to render the system finite at any temperature. Numerical solutions
for the thermal propagators are presented and compared to highprecision
lattice data. To study the deconfinement phase transition, we adapt the
formalism to background gauge and compute the effective action of the
Polyakov loop for the colour groups SU(2) and SU(3). Using the zerotemperature
propagators as input, all parameters are fixed at T=0 and we find a clear signal
for a deconfinement phase transition at finite temperatures, which is second
order for SU(2) and first order for SU(3). The critical temperatures obtained
are in reasonable agreement with lattice data. Continuing this investigation,
we study thermodynamics and, in particular, the pressure of the YangMills
system, and compare to both lattice data and the results of the nonconvariant
Hamiltonian approach. Finally, we briefly discuss the inclusion of fermions and
possible ways to extended our method beyond the Gaussian ansatz.
This report is devoted to the study of the QCD phase diagram with nonzero chiral chemical
potential within lattice simulation. In particular, it is studied the question how nonzero
chiral chemical potential influences the transitions: confinement/deconfinement and
breaking/restoration of chiral symmetry. The results of the calculation can be
explained by the phenomenon which we called chiral catalysis. This phenomenon
is based on the fact that the chiral chemical potential plays a role of the catalyst
of dynamical chiral symmetry breaking.
Studies of the QCD phase diagram at finite temperature and quark chemical potential are currently one of the most discussed topics in theoretical physics and are of great importance to better our understanding of heavyion collision experiments. However, there is considerable uncertainty about the detailed structure of the QCD phase diagram at high baryon densities. Models provide some insight into the phase structure but usually rely on various parameters and therefore require validation from the point of view of the fundamental theory. We propose to apply nonperturbative functional Renormalization Group methods (FRG) to QCD in order to determine constraints on the parameters used in lowenergy QCD models. In particular, this includes a determination of the dependence of these parameters on temperature and quark chemical potential. We present first results and argue that our findings can be used to improve the predictive power of model calculations.
We investigate Landau gauge $SU(3)$ YangMills theory in a
systematic vertex expansion scheme for the effective action with
the functional renormalisation group.
Particular focus is put on the dynamical creation of the gluon mass
gap at nonperturbative momenta and the consistent treatment of
quadratic divergences. The nonperturbative ghost and transverse
gluon propagators as well as the momentumdependent ghostgluon,
threegluon and fourgluon vertices are calculated selfconsistently
with the classical action as only input. The apparent convergence of
the expansion scheme is discussed and within the errors, our
numerical results are in quantitative agreement with available
lattice results.
A massive expansion, based on massive freeparticle propagators,
can be set up from first principles[13] and shown to be
a powerful variational tool disguised to look like a perturbative approximation[3].
By its optimization, the method provides an analytical tool for exploring the
propagators of QCD deep in the infrared of Minkowski space[3] and from first principles,
without having to alter the Landau gauge FaddeevPopov Lagrangian in any way.
The expansion is safe in the infrared and is equivalent to the standard perturbation theory in the UV[2,3].
At oneloop, all diverging mass terms cancel exactly without spurious mass counterterms that
would spoil gauge and chiral symmetry of the Lagrangian.
Gluon mass generation and dynamical breaking of chiral symmetry are described in the
same framework.
The propagators emerge as analytic functions and can be easily studied in Minkowski space, shading some
light on analytic properties that could be hardly explored by numerical methods.
Among the main findings, universal scaling properties are predicted for the inverse dressing functions and
shown to be satisfied by the lattice data that collapse on a universal function, irrespective of couplings,
number of colors and of quarks. Direct evidence is given for positivity violation and confinement of gluons and
quarks. Complex conjugated poles are found for the gluon propagator, in agreement with the iparticle scenario[4]. The relatively small contribution of the
continuos gluon spectral function explains the phenomenological success of simple treelevel
rational propagators that arise in the refined GribovZwanziger[5] and replica models[6].
[1] F. Siringo, Perturbative study of YangMills theory in the infrared, arXiv:1509.05891.
[2] F. Siringo, Analytical study of YangMills theory in the infrared from first principles, Nucl.Phys.B907, 572 (2016); arXiv:1511.01015.
[3] F. Siringo, Analytic structure of QCD propagators in Minkowski space,
arXiv:1605.07357
[4] L. Baulieu, D. Dudal, M. S. Guimaraes, M. Q. Huber, S. P. Sorella, N. Vandersickel, D. Zwanziger, Phys.Rev.D82, 025021 (2010).
[5] D.Dudal, S.P.Sorella, N.Vandersickel, H.Verschelde, Phys.Rev.D77, 071501 (2008).
[6] S. P. Sorella, J.Phys.A44, 135403 (2011).