### Conveners

#### Section B

- Jose Luis Goity (Hampton University/Jefferson Lab)

#### Section B

- Nikolaos Stefanis (Ruhr University Bochum, Germany)

#### Section B

- Hagop Sazdjian (University Paris-Sud)

#### Section B

- Nikolaos Stefanis (Ruhr University Bochum, Germany)

#### Section B

- Jose Luis Goity (Hampton University/Jefferson Lab)

#### Section B

- Hartmut Wittig (JGU Mainz)

#### Section B

- Jose Luis Goity (Hampton University/Jefferson Lab)

#### Section B

- Chueng Ji (North Carolina State University)

#### Section B

- Nikolaos Stefanis (Ruhr University Bochum, Germany)

#### Section B

- Hagop Sazdjian (University Paris-Sud)

### Description

Section B: Light Quarks

Chiral and soft collinear effective theories; sum rules; lattice; Schwinger-Dyson equations; masses of light quarks; light-quark loops; phenomenology of light-hadron 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 light-front 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 light-front dynamics and the advantage of

the light-front dynamics in hadron physics. As an application, we present our recent work on the flavor asymmetry in the proton sea and identify...

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 single-hadron and hadron-hadron 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 ...

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 sigma-terms and compare the results obtained recently within lattice QCD.

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...

A precise understanding of low-energy pion-nucleon interactions is central for many areas in nuclear and hadronic physics, ranging from the scalar couplings of the nucleon to the long-range part of two-pion-exchange potentials and three-nucleon forces in Chiral Effective Field Theory. We present a calculation that combines the general principles of analyticity, unitarity, and crossing symmetry...

Bernhard Ketzer [Bernhard.Ketzer@cern.ch]

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...

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...

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...

We consider the predictions and estimate systematically all theoretical uncertainties

of pion-photon transition form factor using the light-cone sum rules at low-mid

momenta-transfer.

The low energy (below ~2 GeV) pi-eta 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 (q-bar q) states i.e. a0(980) and a0(1450)....

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 time-like region from ~1 million fully reconstructed pi0 Dalitz decay is presented....

Results of a sophisticated approach to a comprehensive meson phenomenology within the

rainbow-ladder truncated Dyson-Schwinger--Bethe-Salpeter equation framework are presented

and discussed.

The exotic and non-exotic light and heavy quarkonium mass spectrum in the

spin-0 and spin-1 channel, as well as for tensor mesons is evaluated.

Quasi-exotic counterparts of exotic quarkonia in the...

In this talk we present the Two-hadron 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...

The concept of Generalized Parton Distributions promises an understanding of the generation of the charge, spin, and energy-momentum 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 three-dimensional structure of hadrons. To...

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 Drell-Yan, Semi-inclusive DIS, ee-> 2 hadrons), using effective field theories, performing higher order calculations in...

A gobal effort is ongoing in the study of transverse-momentum 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.

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 quark-antiquark state and baryons as a three quark state—are important since they clarify the limitation of the quark model as...

The non-perturbative 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...

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. four-quark, five-quark) currents, the contribution of the exotic multiquark hadrons to these correlation functions emerge...

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...

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...

A review of familiar results of the three-point Green functions of currents in the odd-intrinsic parity sector of QCD is presented. Such Green functions include very well-known 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...

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...

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...

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...

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

data-driven model-independent approach based on the use of rational approximants applied to

$\pi^{0}, \eta$...

Studies of multi-baryon systems present a formidable challenge to lattice QCD.

The H-dibaryon represents the simplest multi-baryon 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...

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 Dyson-Schwinger equations of QCD. The light pseudoscalar mesons are the best possible case for such considerations as the approach is very well-constrained by symmetries and there is direct connection to...

Three-flavor chiral perturbation theory with $t,b,c$ quarks decoupled tests the infrared limit of three-flavor 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 chiral-scale perturbation theory $\chi$PT$_\sigma$ about a scale-invariant theory where the quark condensate...

The precise SIDDHARTA value of the energy shift and width of kaonic hydrogen has awaken a renewed interest for the meson-baryon interaction in the $S=-1$ sector. Our study has been carried out based on a chiral SU(3) Lagrangian up to next-to-leading order (NLO) and implementing unitarization in coupled channels, since the presence of $\Lambda(1405)$ resonance makes not applicable a...

Recently, the GWU lattice group has evaluated high-precision phase-shift 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 two-flavor lattice...

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...

A myriad of new techniques and technologies made it possible to inaugurate the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory as the world's first high-energy polarized proton collider in December 2001. RHIC delivers polarized proton-proton collisions at center-of-mass energies of up to 500 GeV. This unique environment provides opportunities to study the polarized...

The COMPASS experiment at CERN took the first ever polarized Drell-Yan data in 2015. The muon pairs originating from pion induced collisions provide a way of accessing the transverse

momentum dependent parton distribution functions of the nucleon. The study of the azimuthal spin asymmetries in Drell-Yan complements a wealth of results already obtained from transversely polarized semi-inclusive...

Regular operation of the VEPP-2000 electron-positron collider started at the end of 2010 and about 60 pb$^{−1}$ were collected so far by the CMD-3 detector in the whole available c.m. energy range from 0.32 GeV to 2.0 GeV. These measurements allow improvements in the precision of the predicted value of the muon anomalous magnetic moment. We report here current results of analysis of the...

The main goal of the High Acceptance Di-Electron experiment (HADES) [1] at GSI is the study of hadronic matter in the $1-3.5$ GeV/nucleon incident energy range. The obtained dilepton spectra measured in nucleon-nucleon, nucleon-nucleus and heavy-ion reactions at various beam energies demonstrate important contributions from baryon resonances decays ($R\rightarrow Ne^+e^-$). The...

High-energy peripheral reactions provide an excellent opportunity to study the excitation spectrum of hadrons. The COMPASS experiment at CERN has measured the diffractive scattering of pions to the 3-pion final state with unprecedented statistical precision. Partial wave analysis techniques have been employed to obtain an expansion of the reaction cross section in terms of partial waves with...

I will review activities of the Joint Physics Analysis Center

The goal of the COMPASS experiment at CERN is to study the structure and dynamics of hadrons. The two-stage spectrometer used by the experiment has good acceptance and covers a wide kinematic range for charged as well as neutral particles allowing to access a wide range of reactions. Light mesons are studied with negative (mostly $\pi^-$) and positive ($p$, $\pi^+$) hadron beams with a...

The nucleon excitation scheme has been under intensive investigation with meson photoproduction experiments during the last few years world wide. Currently, a lot of new experimental results are coming out from the CLAS experiment at Jlab, the Crystal Barrel experiment at the ELSA accelerator in Bonn and the Crystal Ball experiment at the MAMI accelerator in Mainz. These experiments focus on...

We report on BESIII measurements of the timelike pion form factor obtained via the initial state radiation technique, the decays of $\eta^\prime$ into the final states $\pi^+\pi^-\gamma$, $e^+e^-\gamma$ as well as the observation of the $\eta^\prime$ decay into $\omega e^+e^-$.

Strong diquark correlations inside baryons is a consequence of two emergent phenomena in Quantum Chromodynamics (QCD): dynamical chiral symmetry breaking and confinement. That is to say, any interaction capable of creating pseudo-Goldstone modes as bound-states of a light dressed-quark and -antiquark, will necessarily also generate strong colour-antitriplet correlations between any two dressed...

The Green's functions of QCD encode the properties of hadrons,

with the appearance of (colour singlet) poles in n-point functions

corresponding to bound-states and resonances. There are several

techniques by which such information may be extracted, including

lattice QCD and functional methods. We discuss recent progress in

applying nPI effective action techniques to the systematic...

By β-decay a Neutron transforms into a Proton and emits a Positron and a Neutrino. The latter only interacts weakly. During Neutron Star formations and mergers, we have a high Neutrino flux, which can be measured. Therefore by Neutrino measurement, we can learn about the inner structure of Neutron Star formations and mergers. Because during these processes the matter is dense, we have a back...

We summarise recent advances on the description of exotic and excited states

using an approach to QCD via Dyson-Schwinger and Bethe-Salpeter equations.

We discuss first steps in the calculation of (quenched) glueball states, explain

in more detail methods and results to extract the spectrum of four-(anti-)quark

states from the four-body Faddeev-Yakubovski equation and present first...

The dual parametrization of of generalized parton distributions (GPDs) and the

Mellin-Barnes integral approach represent two frameworks for handling the double

partial wave expansion of GPDs in the conformal partial waves and in the cross-channel

${\rm SO}(3)$ partial waves. We explicitly show the complete equivalence of these two independently developed GPD representations. This provides...

We compute for first time the spectrum of the Bethe-Salpeter equation, for a system composed of two bosons exchanging a massive scalar. The ladder approximation for the kernel is used. This study is performed directly in the Minkowski space by using the Nakanishi representation of the Bethe-Salpeter amplitude and the projection onto the null plane or light-front projection. The eigenvalues,...