### Conveners

#### Plenary session

- Antoni Szczurek (Institute of Nuclear Physics PAS)

#### Plenary session

- Johan Messchendorp (University of Groningen)

#### Plenary session

- James Ritman (GSI, Jülich, RU Bochum)

#### Plenary session

- Karin Schönning (Uppsala University)

#### Plenary session

- Daniel Brandenburg (Ohio State University)

#### Plenary session

- Béatrice Ramstein (IJCLab)

#### Plenary session

- Catalina Oana Curceanu (INFN-LNF)

#### Plenary session

- Laura Fabbietti (Technical University of Munich)

#### Plenary session

- James Vary (Iowa State University)

#### Plenary session

- Piotr Salabura (Jagiellonian University)

Belle II offers unique possibilities for the discovery and interpretation of exotic multiquark states to probe the fundamentals of QCD. This talk presents recent results on searches for the hidden bottom transition between $\Upsilon(10750)$ and $\chi_{bJ}$, and measurements of the energy dependence of the $e^+e^- \to B^{(*)} \bar B ^{(*)}$ cross section.

I discuss the basic principle as well as typical problems, when computing masses of exotic mesons with lattice QCD. I also present selected recent lattice QCD results for exotic mesons. I focus on systems composed of two heavy anti-bottom quarks and two lighter quarks.

I will highlight recent progress in the applications of functional methods, in particular the combination of Dyson-Schwinger and Bethe-Salpeter equations, to meson structure and dynamics. This includes calculations of light and heavy four-quark states and their mixing with ordinary mesons, studies of light-front dynamics using contour deformations in the complex momentum plane, and progress...

An outstanding puzzle in our study of strong interactions is understanding how the spectrum of mesons arises from Quantum Chromodynamics. There is a growing body of evidence that QCD generates mesons and baryons beyond quark-antiquark and three-quark configurations. In addition, theoretical calculations of the spectrum of mesons predict states with gluonic degrees of freedom that arise from...

Exotic hadrons beyond the simple quark model are allowed for and predicted within quantum chromodynamics. They offer laboratories to study the strong interaction. Experimental searches are performed since decades, however, most of them were not conclusive yet. Since the beginning of the millenium, a new era has begun with the discovery of the so-called charmonium-like (exotic) XYZ states. With...

The Higgs boson is responsible for just 1% of the visible mass in the Universe. Obviously, therefore, Nature has another, very effective way of generating mass. In working toward identifying the mechanism, contemporary strong interaction theory has arrived at a body of fundamental predictions, *viz*. the emergence of a nonzero gluon mass-scale, a process-independent effective charge, and...

I illustrate recent progress in hadron spectroscopy from Lattice QCD. The scope of this presentation will be studies making use of finite-volume methods to determine hadronic scattering amplitudes. I will focus in particular on recent calculations for mesons and baryons whose properties posed a challenge for traditional quark-model calculations.

The Large Hadron Collider beauty (LHCb) collaboration has made significant strides in the study of exotic states of matter. These states, which include particles composed of more than three quarks or with non-quark constituents, challenge our understanding of the strong force and the nature of hadrons. In this talk, we present the latest experimental results from LHCb on exotic states,...

High energy nuclear collisions produce ultra-Lorentz contracted electromagnetic fields which manifest as high energy photons.

The photons from the electromagnetic fields of one nucleus can fluctuates into a $q\bar{q}$ and interacts with the target through a Pomeron - a two gluon state at lowest order. Such photonuclear processes have been known for decades as a probe of the gluon...

Despite mesons being one of the longest known type of particles, there are still many open questions. Besides well understood states that can be clearly attributed to meson nonets, there are many candidates which could have an exotic nature instead. Such exotic particles e.g. glueballs, hybrids and tetraquarks can be especially studied in clean, gluon-rich environments.

The BESIII experiment,...

Over the past two decades, numerous new hadrons have been observed in the charmonium and bottomonium energy regions. Many of these states reside near meson-antimeson thresholds and therefore can be considered as potential candidates for meson molecules. In this talk, I will discuss how to decipher the nature of such states from experimental line shapes and lattice QCD simulations. An overview...

The neutral pion is the lightest two-quarks strongly interacting particle in Nature. As such, the properties of π0 decay are especially sensitive to the underlying fundamental symmetries of quantum chromodynamics (QCD). In particular, the π0 →γγ decay width is primarily defined by the braking effects of axial and chiral symmetries (chiral anomaly) in QCD. Theoretical activities in this domain...

The next generation of electron-hadron facilities has the potential for significantly improving our understanding of exotic hadrons. The $XYZ$ states have not been seen in photon-induced reactions so far. Their observation in such processes would provide an independent confirmation of their existence and offer new insights into their internal structure. I will discuss what are the...

Light-front quantization of a Hamiltonian derived from quantum field theory has a long history. The introduction of Basis Light-Front Quantization (BLFQ) has led to the development of Hamiltonians and numerical methods for solving both relativistic bound state and scattering applications in models linked to QCD. For QCD applications in limited Fock spaces, one assumes a form of confinement...

The discoveries of the pentaquark states and $XYZ$ mesons in the charmed quark sector initiated a new epoch in hadron physics, where the existence of exotic multi-quark states beyond the conventional three and two quark systems has been unambiguously realised. Similar structure may be evidenced in the light, $uds$ sector in meson photoproduction, where access to a low momentum exchange and...

At SPring-8 LEPS2 beamline, a linearly polarized photon beam is available in the tagged energy range of 1.3–2.4 GeV. The first stage of LEPS2 project was carried out using an experimental setup with a large acceptance calorimeter, called BGOegg, which had the world’s best resolution in the energy range around 1 GeV. So far, we have intensively studied for the origin of hadron mass via...

We summarise recent theoretical results on the QCD phase diagram and the properties of hadrons at finite temperature and chemical potential based on a combination of lattice QCD and Dyson-Schwinger equations. We discuss the silver blaze property of mesons with different quantum numbers along the zero-T-finite-mu-axis and assess the influence of meson and baryon fluctuations on the location...

We present recent results on the in-medium spectral function of the rho(770) vector meson and the a1(1260) axial-vector meson in nuclear matter, as well as on the resulting thermal dilepton rate. As an effective description of the thermodynamics and the phase structure of nuclear matter we use a chiral baryon-meson model, taking into account the effects of fluctuations from scalar mesons,...

The High Acceptance Di-Electron Spectrometer (HADES) [1], installed at GSI Helmholtzzentrum in Darmstadt, was designed for spectroscopy of positron-electron pairs in heavy-ion reactions in the SIS-18 energy range (1-2 GeV/nucleon). HADES results on e+e- production in proton-nucleus and nucleus-nucleus systems at various energies reveal a strong enhancement of the e+e- yield...

The J-PARC Hadron Experimental Facility was constructed with an aim to explore the origin and evolution of matter in the universe through the experiments with intense particle beams. In the past decade, many results on particle and nuclear physics have been obtained at the present facility. To expand the physics programs to unexplored regions never achieved, the extension project of the Hadron...

Meson-nucleus bound states, such as mesic atoms and nuclei, are important topics in hadron physics as they provide valuable information on the properties of hadrons at finite nuclear density. For example, deeply-bound pionic atoms have been intensively studied with missing-mass spectroscopy of the (d,3He) reaction and have led to the experimental evaluation of partial restoration of chiral...

The so-called hadronization is a non-perturbative QCD phenomenon corresponding to the formation of colourless hadrons from coloured quark constituents. The hadron formation in point-like $e^+e^-$ collisions is described via the Lund string fragmentation, according to which the $q\bar{q}$ pair production in the scattering is followed by a shower of light partons produced via multiple...

In this talk, we discuss the recent theoretical studies of the strong interaction between an antikaon ($\bar{K}$) and a nucleon ($N$) [1,2]. The isospin $I=0$ channel is of particular interest, as it exhibits an attractive interaction that can generate a quasi-bound state known as the $\Lambda(1405)$ resonance, located below the $\bar{K}N$ threshold. This suggests that the $\bar{K}N$...

The residual strong interaction for two-body hadron systems has successfully been studied

with an innovative technique at the LHC by the ALICE collaboration in recent years.

Correlation in momentum space measured in pp and p-Pb collisions at the LHC energies for several hadron pairs involving strange hadrons have been employed to test the strong interaction with unprecedented precision....

Studies of hypernuclei, subatomic bound systems with at least one hyperon, have been contributing for understanding the fundamental baryonic interactions as well as the nature of dense nuclear matters. Hypernuclei can also reveal nature of ordinary sub-atomic nuclei by using a hyperon as a prove or/and an impurity in nuclei. Hypernuclei have already been studied for almost seven decades in...

The interaction energy between Λ hyperons and the presence or absence of Ξ hypernuclei (is Ξ hyperons bound to the nuclei?), which can be obtained from doubly-strange hypernuclei, are essential information for a unified understanding of baryons under SU(3)_{f} symmetry. Especially in recent years, they are also valuable information for understanding the existence of...

Today, the most important experimental information missing in the field of the low-energy antikaon-nucleon interactions is the experimental determination of the hadronic energy shift and width of kaonic deuterium measurement that will be performed by the new SIDDHARTA-2 experiment, which just finished the installation in DAFNE and is ready to start a new data taking campaign.

The precise...

The speed of sound in the core of neutron stars is a key quantity for providing a characteristic signature of a possible phase transition or the occurance of non-standard degrees of freedom in dense baryonic matter. The first part of this talk presents a status summary of results from a systematic Bayes inference analysis of the equation-of-state based on observational data. In the second part...

Understanding the dynamics of hadrons with strangeness has received a lot attention over the past decades in connection with the study of exotic atoms, the analysis of strangeness production and propagation in particle and nuclear research facilities, and the investigation of the possible strange phases in the interior of neutron stars.

In this talk I will review the dynamics of strange...

I will discuss the recent results from JLab on J/\psi photo production and prospects and exceptions for exotic charmonia at future photon-/lepton- machines

A lot of progress has recently been made in a field of hadron spectroscopy. Intense photon beams complemented by high-resolution hermetic 4pi detectors, supplied with linearly or circularly polarised photons, polarised nuclear targets and ability to detect recoil nucleon polarisation improved our knowledge on excited nucleon states considerably. Most of the progress has been achieved in N* and...

The CEBAF accelerator complex at Jefferson Laboratory has been delivering precise electron beams with energies up to 12 GeV for several years now. I will review the results to date, with an emphasis on meson spectroscopy and dynamics, and provide an outlook for measurements from approved experiments that will run in the next several years.

This talk will present a brief status review of the anomalous magnetic of the muon (g-2), highlighting the recent progress in experiments, lattice QCD simulations, and Standard Model theories to understand the hadronic contribution to the muon g-2, namely the hadronic vacuum polarization (HVP) and hadronic light-by-light scattering (HLbL). Both are the major sources of theoretical uncertainty...

In spite of the variety of attempts to create dark matter at accelerators, up-to-now, none of the conducted experiments has produced any evidence.

This elusiveness of dark-matter has then triggered innovative and open-minded approaches spanning a wide range of energies with high-sensitivity detectors [1].

In this scenario is inserted the Positron Annihilation into Dark Matter Experiment...

The NA62 experiment at CERN collected the world's largest dataset of charged kaon decays in 2016-2018, leading to the first measurement of the branching ratio of the ultra-rare $K^+ \rightarrow \pi^+ \nu \bar\nu$ decay, based on 20 candidates. In this talk the NA62 experiment reports recent results from analyses of $K^+ \rightarrow \pi^0 e^+ \nu \gamma$, $K^+ \rightarrow \pi^+ \mu^+ \mu^-$ and...

KLOE and KLOE-2 data are the largest dataset ever collected at an electron-positron collider operating at the $\phi$ resonance peak (almost 8 fb$^{-1}$).

The data corresponds to the production of about 24 billion of $\phi$ mesons, namely 8 billion pairs of neutral K mesons and 300 million $\eta$ mesons.

A wide hadron physics program, investigating rare meson decays, $\gamma\gamma$...