New Perspectives on exotic and heavy hadrons

25 Aug 2026, 11:30 → 28 Aug 2026, 18:00 Asia/Seoul

Room 106, 60th Anniversary Hall (Inha University)

Jung-Keun Ahn , Yongwoo Choi , Samson Clymton , Ki-Hoon Hong , Hee-Jin Kim , Hyun-Chul Kim , Shin-Hyung Kim , Seung-il Nam , Nurmukhammad Rakhimov , Sunyoung Ryu , Ulugbek Yakhshiev , Ghil-Seok Yang

Since the Belle Collaboration reported the existence of a possible tetraquark state, X, and the LHCb Collaboration announced new heavy pentaquark states, Pc, there has been a surge of experimental and theoretical efforts to understand the true nature of these exotic hadrons. Since then, more than seventy new heavy hadrons have been observed, including many exotic ones. Interestingly, the GlueX experiment at Jefferson Laboratory reported null results regarding the existence of Pc in J/ψ photoproduction, implying that heavy pentaquarks may possess a nontrivial quark–gluon structure.Recently, various experimental programs aimed at investigating exotic hadrons have been proposed at several accelerator facilities. For example, a new program to measure the Pc in J/ψ production using a pion beam is currently underway at J-PARC. Upcoming novel results on heavy exotic baryons are also expected from the LHC, BESIII (China), and Belle & Belle II (Japan). In this context, we aim to provide an opportunity to gather and discuss the prospects for the future of exotic and heavy hadron research. This workshop will serve as a platform to share both experimental and theoretical ideas and insights related to the physics of exotic states. We will also emphasize the active involvement of young scientists as organizers and speakers, paving the way for the next generation of hadronic physics in the Asian region. 

 

This workshop is sponsored by

 

             

1st circular.pdf

final circular.pdf

Tuesday, 25 August

Registration

Opening

Session 1 - Overview and exotic hadron spectroscopy

1 Exotic hadrons with strangeness

A key issue in understanding hadron structure and quark confinement is the unquenching dynamics, i.e., quark-antiquark pair creation and annihilation in the hadrons. The exotic multi-quark states play an important role for the study of the unquenching dynamics. While the discoveries of exotic hadrons with heavy flavors convinced people the existence of multiquark states, the light quarks play more important role for unquenching dynamics in reality, but are more difficult to deal with. The strange quarks may play a crucial role to bridge the gap between heavy and light quarks. In this talk, I will present recent progresses and prospects on the study of various exotic hadrons with strangeness.

Speaker: Prof. Bing-Song Zou (Tsinghua University)

Exotic-ssbar-Korea-zoubs.pdf

2 Exotic Hadron Spectroscopy with Hadron Beams

This talk provides an overview of experimental searches for exotic baryon states, such as light pentaquark and hexaquark states, including $\Theta^+$, $P_{s\bar{s}}$, $P_{c\bar{c}}$, and $ H$-dibaryons, utilizing hadron beams. Special attention will be given to upcoming experiments at the hadron hall of J-PARC and the KLF at JLab. The talk will also highlight a proposed experiment to study $P_{c\bar{c}}$ states in pion-induced reactions near threshold.

Despite extensive experimental searches using various reactions, light pentaquark states have not yet been discovered. This talk will revisit the upper limits on the existence of the $\Theta^+$ established by high-statistics CLAS measurements, which rule out earlier claims of positive evidence. In combination with other upper limits from pion- and kaon-induced reactions, constraints on the $KN\Theta^+$ coupling constants will also be discussed. Accordingly, new experiments are being considered to search for the $\Theta^+$ in $K^+p$ and $K^+d$ reactions at J-PARC and in $K^0p$ reactions at JLab.

Searches for hidden-strangeness pentaquark states ($P_{s\bar{s}}$) have also been conducted in various reactions, including $\phi$ photoproduction near threshold. Unlike the $\Theta^+$, which occupies the apex of the antidecuplet formed by pseudoscalar meson and baryon octet members, the $P_{s\bar{s}}$ states constitute an isospin doublet within the antidecuplet involving vector meson and baryon octet members. Additionally, the $P_{s}$ states, potentially formed by $\phi\Lambda$ or $\phi\Sigma$, will be searched for in analogy to the $P_{cs}$ state. This talk will address the experimental prospects at J-PARC, where a series of experiments is planned to study the $P_{s\bar{s}}$ and $P_s$ states using hadron beams.

The advent of high-momentum hadron beamlines at J-PARC enables new studies of hidden-charm pentaquark states ($P_{c\bar{c}}$), particularly in the $\pi^-p\to J/\psi n$ reaction. The availability of a separated $K^-$ beam above 10 GeV$/c$ creates opportunities to investigate $P_{c\bar{c}}$ states in the $K^-p\to J/\psi p K^-$ reaction, which shares its final state with the $\Lambda_b\to J/\psi pK^-$ decay. Furthermore, the $K^+p\to J/\psi p K^+$ reaction offers a cleaner channel for studying $P_{c\bar{c}}$, as it avoids complications from hyperon resonances. This talk will explore the prospects presented by these new experimental opportunities using hadron beams.

Speaker: Prof. Jung-Keun Ahn (Korea University)

3 Recent results on exotic and heavy hadrons from Belle II experiment

In Belle II, various exotic and heavy hadrons can be produced in $e^+e^-$ collisions at and near the $\Upsilon(4S)$ resonance. I will report recent results from the Belle II experiment.

Speaker: Kiyoshi Tanida (Japan Atomic Energy Agency)

Inha2026-0825-tanida.pptx

4 Two pion emissions decays of radially excited quarkonia and interactions

Two pion emission decays of radially excited quarkonia are investigated, including Upsilon(3S->1S, 2S; 2S->1S) and Psi(2S->1S). The coupling structure is of scalar-isoscalar type, and the strengths turn out to be in a similar order, implying a common mechanism in the couplings. Using transition matrix elements between these states, we obtain the J/psi-J/psi-2pi couplings, from which we provide J/psi-N potential. We find that the potential is attractive with strength similar to that obtained in lattice simulations.

Speaker: Prof. Atsushi Hosaka (RCNP)

5 Nuclear Gravitational Form Factors

Gravitational form factors of nuclei are calculated in the relativistic mean field theory.
We compute the mass radius and other radii associated with the energy momentum tensor
for doubly-closed nuclei and their isotopes. We also compute the D-term of these nuclei,
the forward limit of the gravitational form factor $D(t=0)=D$.
The mass-number dependencies of the mechanical radii and D-term are discussed.
Our work for the first time elucidates the strong sensitivity of the various
mechanical properties of nuclei to the nuclear shell structure.

Speaker: Prof. Makoto Oka (RIKEN)

6 Maximum-Entropy Reconstruction of Zero-Skewness Valence GPDs from Nucleon Form Factors

We develop a reduced-profile maximum-entropy framework for reconstructing zero-skewness valence-quark generalized parton distributions from the proton and neutron electromagnetic form factors. Since elastic form factors constrain only x-integrated moments, the entropy functional is used as a regularizer within a low-dimensional profile ansatz. A numerical proof-of-concept shows that the reconstructed profiles reproduce the imposed form-factor constraints and yield impact-parameter distributions exhibiting the expected transverse shrinkage at large x. This method provides a stable baseline for future analyses using empirical form factors, modern PDFs, lattice-QCD results, and hard exclusive observables.

Speaker: Prof. Seung-il Nam (PKNU)

15:45 Coffee Break

Session 2 - Pentaquarks and J-PARC searches

7 A New Search for the Θ+ Pentaquark via the d(K+, p)X Reaction at J-PARC

Recent observations of pentaquark candidates in the hidden-charm sector have renewed interest in exotic baryons beyond the conventional three-quark picture. We propose a new search for a narrow pentaquark state with strangeness S = +1 using missing-mass spectroscopy of the d(K⁺, p)X reaction at J-PARC. The K1.8 beamline spectrometer and the high-resolution S-2S spectrometer will precisely measure the momenta of the incident kaon and outgoing proton, respectively, enabling a sensitive search for a narrow structure in the missing-mass spectrum. In this talk, we will present the experimental concept and the current status of feasibility studies.

Speaker: Prof. Shin-Hyung Kim (Kyungpook University)

8 Doubly Heavy Baryons and Pentaquarks in the Pion Mean-Field Picture

We study doubly heavy baryons and pentaquarks in the pion mean-field picture. In this description, the two heavy quarks form a compact core, while the light quarks are described by a pion field. The approach provides a good description of the observed doubly charmed baryons and allows us to estimate the masses of unobserved charmed and bottom baryons. Applying the same framework to doubly heavy pentaquarks, we predict the lightest charmed states at about (3.9)–(4.0) GeV and their bottom counterparts at about (10.2) GeV.

Speaker: June-Young Kim (INHA university)

9 Open-Charm Decay Patterns of the \(P_c(4312)\), \(P_c(4440)\), and \(P_c(4457)\) in the Quark-Interchange Model

The hidden-charm pentaquark structures (P_c(4312)), (P_c(4440)), and
(P_c(4457)) lie close to the (\Sigma_c \bar{D}^{()}) thresholds and are
frequently interpreted as hadronic molecular candidates. We investigate their
open-charm decay patterns by treating these states as (S)-wave
(\Sigma_c \bar{D}^{()}) configurations. The short-range transitions
%
[
\Sigma_c \bar{D}^{()}
\rightarrow
\Lambda_c \bar{D}^{()},
]
%
leading to the (\Lambda_c \bar{D}) and (\Lambda_c \bar{D}^{*}) final
states, are evaluated within the Born-order quark-interchange model. The
transition amplitudes are constructed from the relevant prior and post
quark-rearrangement diagrams, including their spin, flavor, color, and spatial
matrix elements.

The results exhibit a pronounced channel hierarchy: the
(\Lambda_c \bar{D}^{}) mode is generally favored, whereas the
(\Lambda_c \bar{D}) contribution is strongly suppressed. For the
(\Sigma_c \bar{D}^{}) molecular candidates, the predicted decay patterns
are sensitive to the (J^{P}=\frac{1}{2}^{-}) and
(J^{P}=\frac{3}{2}^{-}) assignments. In particular, the (L=0) transition
to (\Lambda_c \bar{D}) vanishes for the (J^{P}=\frac{3}{2}^{-})
assignment within the present treatment. These spin-dependent patterns
indicate that open-charm final states can provide complementary information
for distinguishing possible molecular assignments of the observed (P_c)
structures. The calculated partial widths represent the short-range
quark-interchange contributions; long-range mechanisms and coupled-channel
effects are not included.

Speaker: Vandan Patel (Sardar Vallabhbhai National Institute of Technology Surat, Gujarat, India)

10 Radiative decays of dynamically generated pentaquarks in the chiral unitary approach: the Pc(4457) -> Pc(4312) γ transition

We analyze the radiative decay $P_c(4457)(3/2^-) \to P_c(4312)(1/2^-)\gamma$ by treating both pentaquark states as $S$-wave hadronic molecules. Using a chiral unitary approach with heavy-quark spin symmetry, we calculate photon couplings to meson-baryon components via nineteen $M1$ triangle loops. The transition is dominated by the $\bar D^{*0}\to\bar D^{0}\gamma$ loop, yielding a pure $M1$ transition ($E_\gamma = 143$~MeV) with a central width of $6.7$~keV (ranging between $2$ and $9$~keV). Introducing a soft Gaussian form-factor on the leading diagram reduces the full width to $\sim 4$~keV. We estimate the cascade rate for $\Lambda_b^{0}\to J/\psi\,p\,K^{-}\gamma$ and propose the pure $M1$ content, binding-energy dependence, and decay ratio compared to the $P_c(4440)$ as critical tests of these states' molecular nature.

Speaker: Prof. Daris Samart (Khon Kaen University)

11 Production Mechanism of the Hidden-Charm Pentaquark

The LHCb collaboration's discovery of pentaquarks has revitalized interest in heavy exotic baryon spectroscopy, motivating extensive searches for new states. In this work, we investigate hidden-charm pentaquark states in heavy meson and singly heavy baryon systems by employing an off-shell coupled-channel formalism. The interaction kernel is constructed from meson exchange diagrams using an effective Lagrangian that respects both heavy quark spin symmetry and hidden local symmetry. In this talk, I will present our study of the production mechanisms of hidden-charm pentaquark states ranging from $S=0$ to $S=-3$ in strangeness. Several key findings will be discussed: the suppression of $P_{c\bar{c}}$ signals in $J/\psi$ photoproduction; the two-pole structure of $P_{c\bar{c}s}(4459)$; predictions of $I=3/2$ $P_{c\bar{c}}$ and $I=1$ $P_{c\bar{c}s}$ states; and predictions of eight $P_{c\bar{c}ss}$ and two $P_{c\bar{c}sss}$ states. These findings provide insights into the production dynamics and properties of pentaquark states while offering predictions that can guide future experimental observations.

Speaker: Dr Samson Clymton (APCTP)

18:20 Welcome Reception

Wednesday, 26 August

Session 3 - Production reactions

12 Production of vector mesons in meson-induced reactions

We investigate vector-mesons production off the nucleon within a hybrid Regge approach based on effective Lagrangians. We simultaneously examine total and differential cross sections and spin-density matrix elements. Such measurements could be carried out in future high-intensity poin- and kaon-beam experiments at facilities such as J-PARC. The results of this study may help to shed light on the spectroscopy of high-mass nucleon and hyperon resonances.

Speaker: Dr Sangho Kim (Soongsil University)

13 Hadronic production of the phi meson in pi- p to phi n near threshold

We investigate the hadronic production of the $\phi$ meson in the OZI-suppressed reaction $\pi^- p \to \phi n$ near threshold within an effective Lagrangian framework. Since the $\phi$ meson is predominantly an $s\bar{s}$ state, its direct coupling to the nucleon is expected to be strongly suppressed at the quark level. However, intermediate hadronic channels and baryon resonances can generate sizable $\phi N$ interactions, making this reaction an ideal probe of the underlying reaction mechanism, the $\phi N$ interaction, and possible hidden-strangeness pentaquark states.

The reaction amplitude is constructed from the $s$-, $u$-, and $t$-channel diagrams with nucleon, $N^*$ resonance, and meson-exchange contributions. The model satisfies the extended Ward-Takahashi identity within the hidden local symmetry framework, and Reggeized propagators are introduced to describe the reaction at moderately high energies.

Our preliminary results indicate that the $N^*$ resonances play an important role in reproducing the observed near-threshold behavior, while the $t$-channel contribution becomes increasingly significant at higher energies. In addition to the total and differential cross sections, we investigate the spin-density matrix elements (SDMEs) of the produced $\phi$ meson in the helicity and Gottfried-Jackson frames. These polarization observables provide complementary information for identifying the underlying reaction mechanisms beyond cross-section measurements. The remaining discrepancies in the forward-angle region suggest that further investigation of the $t$-channel contributions and comparison with more precise experimental data will be necessary.

Speaker: Dayoung Lee (PKNU)

14 Production Mechanism of the \chi_{cJ} and \psi_J states

We investigate the dynamical generation of isoscalar charmonium-like
states with a coupled-channel approach. Our focus is placed on states
with quantum numbers $J^{PC}=0^{++}$, $1^{++}$, $2^{++}$, and $3^{--}$
in the mass range of 3.6 to 4.3 GeV. We describe these systems through
effective Lagrangians constrained by heavy-quark spin-flavor and
chiral symmetries, employing an off-shell Blankenbecler-Sugar
formalism. Our study reveals six dynamically generated poles in the
complex energy plane. Among them, the experimentally observed
$\chi_{c1}(3872)$ is successfully reproduced as a bound state near the
$D\bar{D}^*$ threshold. In addition, we find a scalar ($0^{++}$)
resonance at 3861 MeV and a broader axial-vector ($1^{++}$) resonance
at 3961 MeV, alongside bound states below the $D\bar{D}$ and
$D\bar{D}^*$ thresholds. Furthermore, we identify a narrow tensor
($2^{++}$) pole at 4005 MeV and a negative-parity $\psi_3$-like
($3^{--}$) state above the $D^*\bar{D}^*$ threshold, which emerge
through dynamical coupled-channel interactions without $s$-channel
pole contributions. These results highlight the crucial role of
coupled-channel dynamics, particularly involving the $D^*\bar{D}^*$
channel, in shaping the spectrum of charmonium-like exotic states.

Speaker: Hee-Jin Kim (Inha University)

15 $J/\psi$ Production in $\pi^-p$ Reaction near Threshold

We present Proposal P111 for a new experiment that will investigate $J/\psi$ production in $\pi^-p$ reactions near threshold at the $\pi$20 beamline of J-PARC. Studying $J/\psi$ production in $\pi^−p$ collisions will offer valuable insights into the mechanism of $c\bar{c}$ pair creation in pion-induced reactions, with particular focus on hidden-charm pentaquark states. This measurement seeks to deliver the world’s first data on total and differential cross sections for the exclusive $\pi^-p\to J/\psi n$ reaction from threshold up to W = 4.65 GeV, thereby spanning the full mass region for $P_c$ states—from $\bar{D}\Lambda_c$ to $\bar{D}^\ast\Sigma^\ast_c$ thresholds. Polarization measurements will also be possible. The P111 proposal includes the development of a dedicated lepton detector for measuring $J/\psi$ leptonic decays, to be incorporated into the MARQ spectrometer. This presentation will highlight the current status and future prospects of the proposal.

Speaker: Prof. Sun-Young Ryu (RCNP)

10:40 Coffee Break

Session 4 - Photoproduction and hadron-hadron interactions

16 Low-energy $N\phi$ scattering from a pole-enhanced triangle diagram

We investigate low-energy $N\phi$ scattering driven by a pole-enhanced triangle-like diagram, in which the two-Kaon-exchange contribution is promoted by the near-threshold $\Lambda(1405)$ pole in the $N\bar K$ subsystem. Using an unphysical Kaon mass motivated by lattice simulations, we evaluate the $N\phi$ scattering length and find that this mechanism generates an attractive interaction with a magnitude of $-1.1$ to $-0.5\, \rm{fm}$. Spin-dependent effects are not treated explicitly and are expected to provide subleading corrections in the near-threshold region. We further analyze the low-energy behavior of the triangle-like diagram amplitude and show that the scattering length depends on the parameter $\delta$, defined as the mass difference between the $K\bar K$ threshold and the $\phi$ meson, and the pole position of $\Lambda(1405)$, where the $\Lambda(1405)$ plays a crucial role to understand $N\phi$ interaction. Furthermore, by employing physical hadron masses, our calculated scattering length is found to be consistent with current experimental data, providing a unified description across both unphysical and physical mass regimes. This type of interaction differs from that associated with van der Waals-type forces or the long-range tail of two-pion exchange, highlighting the role of three-body dynamics encoded in the pole-enhanced triangle-like diagram in shaping the near-threshold $N\phi$ interaction.

Speaker: Mao-Jun Yan (Southwest University)

Nphi_Maojun.pdf

17 Understanding Near-Threshold Vector-Meson Photoproduction for Exotic-Hadron Searches and Gravitational Form Factors

Near-threshold vector-meson photoproduction offers a promising way to investigate both exotic-hadron production and the internal structure of hadronic and nuclear targets. In particular, (J/\psi) photoproduction has attracted considerable attention as a possible channel for searching for hidden-charm pentaquark states and as a probe of the gravitational form factors of the proton. However, the interpretation of such measurements depends critically on our understanding of the underlying photoproduction mechanisms.

In this talk, I will discuss near-threshold (\phi) and (J/\psi) photoproduction from proton and nuclear targets. Comparing hidden-strangeness and hidden-charm production may help clarify the roles of different production mechanisms and threshold effects. Reactions on the proton and coherent reactions on (^{4}\mathrm{He}) also provide complementary information for separating properties of the production process from those of the target. I will discuss how a better understanding of these reactions can contribute both to searches for exotic hadrons and to studies of gravitational form factors and the mechanical structure of hadrons and nuclei. Possible observables and remaining theoretical challenges will also be addressed.

Speaker: Keigo Mizutani (RCNP, The University of Osaka)

18 Entanglement suppression for K\bar{K} scattering

The S-matrix describing the scattering process can be expressed in terms of projection operators onto the allowed spin–isospin channels and the corresponding phase shifts. Using the entanglement entropy in the spin or isospin space of the two-particle state, one can define the entanglement power, which quantifies the ability of the S-matrix to generate entanglement in the system. By investigating the conditions under which the entanglement power of the S-matrix is minimized, namely, the conditions for entanglement suppression, one can derive relations among the phase shifts in different spin-isospin channels. Furthermore, by comparing these relations with the interaction Lagrangian, one can identify the underlying symmetries [1,2].

In this work, we apply the framework of entanglement suppression to coupled-channel meson scattering involving the K\bar{K} system. We discuss the implications of the conditions obtained from entanglement suppression and the structure of near-threshold resonances, such as f_0(980) and a_0(980), from the perspective of emergent symmetries.

[1] S. R. Beane, D. B. Kaplan, N. Klco and M. J. Savage, Phys. Rev. Lett. 122, 102001 (2019).
[2] I. Low and T. Mehen, Phys. Rev. D 104, 074014 (2021).
[3] T.R. Hu, K. Sone, F. K. Guo, T. Hyodo and I. Low, arXiv:2506.08960 [hep-ph].

Speaker: Katsuyoshi Sone (Tokyo Metropolitan University)

12:30 Lunch

Session 5 - Lattice QCD, few-body systems and nucleon structure

19 Five-body structure of udscc-bar

The LHCb collaboration has observed a pentaquark system, $udsc\bar{c}$, with
$J^{\pi} = 1/2^{-}$, whose mass is $4338.2$ MeV with $\Gamma = 7$ MeV [1].
To describe this state, I use a constituent quark model, and the employed
Hamiltonian is based on Semay and Silvestre-Brac [2]. This Hamiltonian
reproduces all of the meson and baryon states which appear in the open channels
of this pentaquark system. For the color wavefunction, we include the excited
effect of color, namely the color octet state. To consider the resonant state of
this pentaquark system, we utilize the real scaling method. The result will be
shown in the workshop.

Reference

[1] S. K. Choi et al. (Belle Collaboration), Phys. Rev. Lett. 91, 262001 (2003).

[2] C. Semay and B. Silvestre-Brac, Z. Phys. C 61, 271 (1994);
B. Silvestre-Brac, Few-Body Syst. 20, 1 (1996).

Speaker: Prof. Emiko Hiyama (Tohoku University / RIKEN)

20 Search for Exotic States in Three-meson Systems

We investigate the three-body $PPV$ and $PVV$ systems, where $P$ denotes a pseudoscalar meson and $V$ denotes a vector meson. The Faddeev equations are solved within the fixed-center approximation, while the underlying two-body $PP$, $PV$ and $VV$ interactions are determined from the chiral unitary approach. Strong interactions among these mesons produce obvious resonance structures in the modulus squared of the three-body scattering amplitude, indicating the possible formation of exotic hadron states. We also conduct a theoretical study of the hidden charm $D\bar{D}K$ three-body system. The obtained results are consistent with previous theoretical predictions and support the presence of an excited hidden-charm kaon state, $K_{c\bar{c}}(4180)$, with quantum numbers $I(J^P) = \frac{1}{2}(0^-)$ and a mass of approximately $4180$ MeV. These findings provide theoretical guidance for future experimental searches for exotic hadrons in three-meson systems.

Speaker: Prof. Ju-Jun Xie (Institute of Modern Physics, Chinese Academy of Sciences)

21 Lattice QCD studies on $KN$/$\bar{D}N$ interactions and search for genuine pentaquarks

Interactions between a nucleon and a meson containing a heavy antiquark, in which quark-antiquark annihilation is absent, have been predicted to be attractive and to form genuine pentaquark states. With realistic lattice QCD simulations for such systems now feasible, first-principles determination of these interactions can provide theoretical prediction for the existence of the pentaquarks.
We investigate kaon-nucleon ($KN$) interaction and its charm-sector counterpart, $\bar{D}$ meson-nucleon ($\bar{D}N$) interaction. The calculation is performed using the configurations at the physical point, $m_{\pi}\approx 137$ MeV. S-wave interaction potentials are extracted via the time-dependent HAL QCD method.
In this talk, I will present the resulting potentials and scattering phase shifts, and discuss the absence of pentaquarks. Furthermore, I will compare the two channels and discuss the underlying physical mechanisms of the interactions.

Speaker: Kotaro Murakami (Institute of Science Tokyo)

22 Nucleon structure and multi-hadron dynamics from lattice QCD

Recent advances in lattice QCD have enabled increasingly precise first-principles calculations of nucleon structure observables. In this talk, I will present recent progress on nucleon electromagnetic and axial form factors, together with flavor-diagonal nucleon charges, with particular emphasis on controlling excited-state contamination. I will discuss data-driven analyses guided by the low-lying $N\pi$ spectrum, highlighting how an inadequate description of excited states can significantly bias the extracted nucleon matrix elements, with important consequences for quantities such as sigma terms, axial form factors, and the PCAC relation. Finally, I will briefly introduce our ongoing preliminary efforts toward lattice studies of multi-hadron systems using multi-hadron operators within the framework of lattice hadron spectroscopy. These efforts provide a natural pathway toward future studies of hadron resonances and more complex hadronic systems relevant to exotic hadron spectroscopy.

Speaker: Prof. Sungwoo Park (Sejong University)

23 Tensor properties of the nucleon in a pion mean-field approach

The tensor form factors of the nucleon carry essential information for understanding its internal spin structure. The monopole tensor form factor at $Q^2=0$ is identified as the nucleon tensor charge, which corresponds to the first moment of the leading-twist transversity distribution $h_1(x)$. While transversity has been studied extensively both in theory and in experiment, the other tensor form factors have attracted far less attention. In this talk, we present recent results for the nucleon multipole tensor form factors obtained within the pion mean-field theory. The framework rests on the effective dynamics arising from spontaneous chiral symmetry breaking and on the mean-field description of the nucleon at leading order in the large-$N_c$ limit. We find that the tensor charge ($g_{T}^{u-d}=0.99$) and the tensor anomalous magnetic moment ($\kappa_{T}^{u+d}=7.61$) are dominated by valence quark contributions, whereas the tensor quadrupole moment ($Q_{T}^{u-d}=-7.02$) exhibits significant sea quark effects. We also explore how these moments depend on the soliton size and the pion mass, observing a smooth transition between the non-relativistic and relativistic regimes. The results agree well with available lattice QCD data and provide predictions for quantities that have not yet been measured.

Speaker: Nam-Yong Ghim (Inha University)

16:05 Coffee Break

Session 6 - Glueballs and antimatter probes

24 Hadron Physics using Antimatter Probes at J-PARC HEF

Antiproton beams provide a unique probe of hadronic matter through gluon-rich annihilation processes, offering exceptional opportunities for spectroscopy of conventional and exotic hadrons as well as studies of hyperon production and baryon-antibaryon dynamics. Following a decades-long decline in medium-energy antiproton facilities, new initiatives at the J-PARC Hadron Experimental Facility are opening promising prospects for a renewed antiproton physics programme.

This presentation will discuss the scientific opportunities enabled by the planned high-momentum beamlines, $\pi20$ and $K10$, which are expected to deliver intense antiproton beams covering the medium-energy region inaccessible to existing facilities. Their broad momentum reach and high beam intensities provide access to a largely unexplored domain for hadron spectroscopy, including strange and charmed hadrons, exotic states, and investigations of non-perturbative QCD in a gluon-rich environment. Physics opportunities beyond hadron spectroscopy, such as precision measurements of antimatter interactions relevant to cosmic-ray experiments, will also be highlighted.

The status of the J-PARC antiproton programme, ongoing beamline developments, and the growing international effort to establish J-PARC as a major centre for medium-energy antiproton physics will be presented, together with perspectives for future experiments and international collaboration.

Speaker: Ken Suzuki

25 Lightest 0^{-+} Glueball as Dominant Constituent of X(2370)

With 10 billion $J/\psi$ events collected at \mbox{BESIII}, the decay of $X(2370)\rightarrow K^{*}(892)^{0}\bar{K}^{0}+\mathrm{c.c.}$ is searched for via the $J/\psi\rightarrow\gamma K_{S}^{0}K_{S}^{0}\pi^{0}$ process. No evidence of this decay mode is found, with $\mathcal{B}[J/\psi\rightarrow\gamma X(2370)] \times \mathcal{B}[ X(2370) \rightarrow K^{*}(892)^{0}\bar{K}^{0}+\mathrm{c.c.} \rightarrow K^{0}_{S}K^{0}_{S}\pi^{0}] < 2.7\times 10^{-6}$ at the $90\%$ confidence level. The suppression of the $K^{*}(892)\bar{K}$ mode indicates the $X(2370)$ as a flavor-singlet state. It is the first flavor-singlet light hadron observed above $1~\GeV/c^{2}$. All \mbox{BESIII} measurements on the $X(2370)$ are summarized. A dominant component of the lightest $0^{-+}$ glueball is essential for a natural and complete explanation of the properties of the $X(2370)$~\textemdash~the mass, spin-parity, high production rate in $J/\psi$ radiative decays, decay pattern similarities to that of $\eta_{c}$, flavor-singlet property, narrow partial decay width, and suppression of radiative decays to $\omega$ and $\phi$, since these properties are all consistent with the features of the lightest $0^{-+}$ glueball while other interpretations at present are disfavored. This supports that the lightest $0^{-+}$ glueball is the dominant constituent of the $X(2370)$.

Speaker: Prof. Yanping Huang (IHEP)

26 Scalar glueball gravitational form factors

In this talk, the current research work on the scalar glueball gravitational form factors within the Skyrme-Faddeev model will be presented, where this model is constructed based on the Hopf topological invariant. Next, a comparison of our interesting findings with other theoretical calculations and lattice QCD simulation results will be presented and discussed.

Speaker: parada hutauruk (SKCM2, Hiroshima University)

17:50 Dinner

Thursday, 27 August

Session 7 - Molecular states and compositeness

27 Compositeness of near-threshold exotic hadrons in the charm sector

Recent experiments have discovered various exotic hadrons near scattering thresholds, stimulating interest in their internal structure. The compositeness is a useful quantity to characterize the hadronic molecular component of eigenstates [1]. In this work, we discuss the compositeness of near-threshold exotic hadrons, especially in the charm sector. We first consider the universal behavior of shallow $s$-wave bound states and apply the framework to near-threshold candidates such as $X(3872)$ and $T_{cc}$ [2]. We then extend the discussion to a near-threshold $p$-wave resonance, focusing on the exotic-hadron candidate $G(3900)$, for which the relation between the pole position and the internal structure is qualitatively different from the $s$-wave bound-state case [3].

[1] T. Kinugawa and T. Hyodo, Eur. Phys. J. A 61, 154 (2025).
[2] T. Kinugawa and T. Hyodo, Phys. Rev. C 109, 045205 (2024).
[3] T. Kinugawa, S. Ampuku, K. Miyake, and M. Oka, in preparation.

Speaker: Tomona Kinugawa (RIKEN)

28 Coupled-Channel Effects on Near-Threshold Exotic States

Understanding the nature of exotic hadrons and the internal structure of near-threshold states remains a major challenge in quantum chromodynamics (QCD). We developed a unified framework combining the Godfrey-Isgur relativized quark model, Hamiltonian effective field theory, and finite-volume lattice QCD inputs to systematically study the properties of both conventional and exotic charmed-strange and hidden-charm states.

Using this approach, we reexamined the long-standing puzzle of the Ds0(2317) and Ds1(2460) mesons. Our analysis reveals that these states receive significant coupled-channel effects from D()K interactions, leading to large mass shifts from their bare c\bar{s} cores. The resulting pole masses and compositeness coefficients are in good agreement with lattice QCD data and experimental measurements, indicating a mixed nature with both compact c\bar{s} and molecular D()K components. In contrast, the higher Ds1(2536) and Ds2(2573) states remain predominantly conventional c\bar{s} mesons. In addition, we also study the decay of Ds1(2460) and Ds1(2536) to Ds\pi\pi, where an exotic candidate state Tcs was discovered. These findings highlight the importance of coupled-channel and core-molecule mixing effects in understanding the spectrum of QCD.

Speaker: Prof. Zhi Yang (UESTC)

29 Five-flavor $udsc\bar{b}$ molecular pentaquarks from heavy-quark and local hidden gauge symmetries

We study a family of genuinely exotic five-flavor molecular pentaquark states containing the five quark flavors $u,d,s,c,b$ that form experimentally accessible hadrons. We construct the meson-baryon interaction from the local hidden gauge symmetry combined with heavy-quark spin symmetry, following the chiral unitary description that reproduces the LHCb hidden-charm strange pentaquarks. Heavy-quark flavor symmetry allows us to obtain the $udsc\bar{b}$ sector by replacing the anti-charm quark in the meson with an anti-bottom quark while keeping the charm quark in the baryon. As a result, we obtain ten threshold-associated isoscalar poles with $J^P=1/2^-,3/2^-,5/2^-$ in the range $7.72$ to $7.96$ GeV. They are narrow and organized into heavy-quark spin multiplets with predicted near-degeneracies. There are four states that overlap with the earlier two-sector study in the literature to about $2$ MeV, which shows that the separate-sector treatment is recovered as a limit of this work. Moreover, we also identify two additional, more deeply bound $B_s\Lambda_c$ and $B_s^{*}\Lambda_c$ poles generated by strong inter-channel coupling because these poles are farther from their dominated thresholds. This is an interesting signal that can be searched for at LHCb in the $B_c\Lambda$ and $B_s^{*}\Lambda_c$ invariant mass spectra.

Speaker: Mr Ratirat Suntharawirat (Khon Kaen University)

10:15 Coffee Break

Session 8 - Heavy hadron spectroscopy

30 Nature of the $\Omega_c$ states: A coupled-channel study of compact and molecular configurations

Recently the LHCb collaboration observed five new narrow excited states in the $\bar{K}\Xi_c$ invariant mass spectrum: the $\Omega_c(3000)$, $\Omega_c(3050)$,$\Omega_c(3065)$, $\Omega_c(3090)$ and $\Omega_c(3119)$. Following this discovery, the Belle Collaboration confirmed four of these five narrow states. A popular interpretation is that the observed $\Omega_c^*$ states correspond to the five $\lambda$-mode excited states in the conventional quark model, which are the p-wave excitations between the charm quark and the two light quarks. However, the spin assignment by the quark model does not follow the experimental data.

In this talk, we show that these new states can be explained as superpositions of meson-baryon molecular states and three-quark bare states through a systematic analysis of the low-lying $\Omega_c$ states using a coupled-channel approach [1]. Our results reproduce the mass spectrum well, and our spin assignments are consistent with the LHCb experimental analysis. We also predict one bound state below the $\bar{K}\Xi_c$ threshold, which is expected to be observed in future experiments.

[1] Y. Zhang, Q.-F. Song, Q.-F. Lü, H. Nagahiro, A. Hosaka, PRD112(2025)034035.

Speaker: Hideko Nagahiro (Nara Women's University)

31 Excited Heavy-Baryon Spectrum from QCD Sum Rules

The experimental observation of a number of excited charmed and bottom baryons has significantly enriched heavy-baryon spectroscopy and provides an important opportunity to study the nonperturbative dynamics of QCD. We classify the P-wave singly heavy baryons according to their flavor representations, internal orbital excitations, and the angular momenta of their light degrees of freedom. Their masses are calculated using QCD sum rules, while their strong and radiative decay properties are studied using light-cone sum rules. By combining the mass spectra with the predicted decay patterns, we investigate possible assignments of the experimentally observed singly heavy baryons.

Speaker: Prof. Hua-Xing Chen (Southeast University)

32 New Spectrum of Charm-Strange Meson

We systematically investigate the spectrum and decay properties of charm-strange mesons using a chiral unitary approach that combines Weinberg-Tomozawa interactions with bare $c\bar{s}$ states from the constituent quark model. The S-wave interactions in the (S,I)=(1,0) sector produce a rich $D_{sJ}$ spectrum with $J^P$=$0^+$, $1^+$, $1^-$, $2^-$. In addition to the well-known $DK$ and $D^* K$ molecular states, we also predict the existence of $D_1 K$ and $D_2 K$ molecular candidates. The decays of these $D_1 K$ and $D_2 K$ states are further studied. Triangle singularities are found to produce narrow peaks in the $D_s^*\pi$ and $D_s\pi$ invariant mass spectra near the $D^* K$ and $DK$ thresholds, respectively. The isospin-violating decays of the $D_1 K$ and $D_2 K$ molecules are predicted to have sizeable partial widths, significantly enhanced by the strong couplings inherent to molecular states. This unified picture, incorporating both molecular and quark-model components, provides phenomenological signatures for identifying these exotic candidates at current experiments.

Speaker: Prof. Xiao-Hai Liu (Tianjin University)

12:00 Lunch

Session 9 - Quark models and effective theories

33 Insights into the composite nature of exotic hadron

Compositeness is an important concept to promote a quantitative understanding of the inner structure for a molecular state. We introduce the compositeness formalism for the case of the resonance, as a generalization of bound-state case. We have also proposed a more general form of two-body scattering amplitude with explicit inclusion of CDD pole, which is more widely applicable than the effective range expansion. Combining those with the experimental input, we get some interesting conclusions that are not found in the previous literature.

Speaker: Prof. Xian-Wei Kang (Beijing Normal University)

34 Hadronic Exceptional Points

Exceptional points (EPs), where eigenvalues and eigenvectors coalesce, are a hallmark of non-Hermitian systems but remain largely unexplored in quantum chromodynamics (QCD). In this talk, we demonstrate that imaginary magnetic fields provide a simple realization of non-Hermitian dynamics in hadronic systems. Using both a hadronic effective Lagrangian and a constituent quark model, we identify EPs in neutral meson spectra that separate the real-spectrum and complex-eigenvalue regimes. Weak fields induce level attraction, while stronger fields lead to hadron deconfinement through an inverted confining potential. These results establish a new connection between non-Hermitian physics and QCD and provide a framework for studying relativistic bound states in non-Hermitian environments.

Speaker: AHMAD JAFAR ARIFI (JAEA)

35 Heavy baryon-antibaryon interactions in a constituent quark model

We study the $\Lambda \overline{\Lambda}$ and $\Lambda_c \overline{\Lambda}_c$ systems in a constituent quark model with color–color, color–spin, and three-quark interactions. The effective baryon–antibaryon interaction is obtained using a variational approach in a constituent quark model. Our results indicate that compact bound states are possible in both strange and charmed sectors, although the attractive interaction becomes weaker for the heavier system. We also discuss the relation between the baryon–antibaryon picture and the corresponding three-meson configurations, which provides further insight into the structure of compact multiquark states.

Speaker: Aaron Park (Yonsei University)

36 Effectvie field theories and nuclear reactions at low energies

Effective field theories (EFTs) are a popular theoretical method in hadron physics and few-body physics. By employing dibaryon fields (or dimer fields) for a two-nucleon system, one can expand the terms around the unitarity limit; the expanded terms are naturally matched to effective range parameters, and the dibaryon (dimer) fields are useful tools to describe bound and resonant states for a two-nucleon system. In this talk, I discuss the application of the dibaryon (or dimer) EFT to the study of nuclear reactions at low energies, for the $\alpha$-$^{12}$C system, and the $n$-$^{16}$O and $\alpha$-$^{13}C systems, where bound and resonant states of nuclei are assigned as dynamical degrees of freedom, and composite fields are employed for them. I discuss the advantages and disadvantages of the method for studying those systems in nuclear physics and nuclear astrophysics.

Speaker: Shung-Ichi Ando (Sunmoon University)

37 Electromagnetic form factors of the nucleon from the instanton vacuum

We investigate the electromagnetic form factors of the nucleon using
an effective chiral theory based on the QCD instanton vacuum.
Here we take into account the momentum-dependent dynamical quark mass
originating from the instanton-induced 2$N_f$ quark interactions.
The momentum-dependent quark mass naturally plays the role of a regulator,
so that no additional regularization is needed. Since the dynamical
quark mass at zero virtuality is fixed by the saddle-point equation beyond
the chiral limit, there is no adjustable free parameter.
Within this framework, we evaluate the proton and neutron electric and
magnetic form factors, charge and magnetization densities, and related
observables. We also compare the results with the chiral quark-soliton model
and the Kelly parametrization. The results are in good agreement with the
experimental data and show that the contributions from the momentum
dependence are not negligible. This study implies that the effective
chiral theory derived from the QCD instanton vacuum gives a consistent
framework to describe the nucleon electromagnetic structure.

Speaker: Hui-Jae Lee (Inha University)

15:35 Coffee Break

Session 10 - Exotic systems, femtoscopy and nucleon structure

38 Femtoscopy and Cusp: New Methods to Study the Hadron-Hadron Interaction

Understanding the complexities of hadron-hadron interactions, particularly in the strangeness sector, is crucial for both hadron physics and the study of dense nuclear matter. Traditionally, these interactions have been investigated through direct scattering experiments, which are inherently limited by the available beam and target channels. To overcome these limitations, two pioneering approaches have recently emerged as indispensable tools: femtoscopy and cusp spectroscopy.

Femtoscopy, which is actively driven by experiments such as LHC-ALICE and RHIC-STAR, has become a powerful method for probing hadronic interactions in high-energy heavy-ion collisions. By measuring two-particle correlations at small relative momenta, femtoscopy at ALICE and STAR provides critical insights into previously inaccessible channels, extracting spin-averaged scattering parameters for various hyperon-nucleon ($YN$) and hyperon-hyperon ($YY$) pairs.

Complementary to this, cusp spectroscopy allows for the precise determination of scattering lengths by analyzing threshold structures. For example, the upcoming J-PARC E90 experiment utilizes the $d(K^{-}, \pi^{-})\Lambda p$ reaction to measure the $\Sigma N$ cusp. By leveraging a deuteron target, this experiment can isolate and determine the scattering length for a specific isospin-spin state, $(T,S)=(1/2,1)$.

This presentation will focus on the strong synergy between these two distinct methods. While femtoscopy provides essential spin-averaged scattering parameters, cusp spectroscopy at J-PARC isolates specific spin configurations. By integrating these results, we can achieve a comprehensive decomposition of all possible isospin-spin states in $\Sigma N$ interactions. Furthermore, we will discuss future prospects for extending these interaction studies, including the upcoming femtoscopy programs at the J-PARC-HI project.

Speaker: Yudai Ichikawa (Tohoku University)

39 Femtoscopy of heavy-flavor hadrons

We study the $D^0\bar{D}^{*0}$ momentum correlation function to clarify the near-threshold structure of $X(3872)$. The $D\bar{D}^*$ interaction is described by a Yamaguchi-type separable potential that includes an effective contribution from a $c\bar{c}$ core. The parameters are fixed to reproduce the observed $X(3872)$ mass. When the pole lies extremely close to the $D^0\bar{D}^{*0}$ threshold, the correlation function in the $J^{PC}=1^{++}$ channel becomes very large at small relative momentum. Bound-state and virtual-state poles near threshold give very similar correlations. Despite the extremely small observed width of the X(3872), its effect on the correlation function is significant. In contrast, the $J^{PC}=1^{+-}$ channel related to $Z_c(3900)$ shows a much smaller correlation, and the effect of the charged $D^+D^{*-}$ channel is modest in the diagonal $D^0\bar{D}^{*0}$ correlation.

Speaker: Prof. Makoto Takizawa (Showa Pharmaceutical University)

40 Production of heavy exotic states in heavy-ion collisions

We study the production of exotic hadrons in heavy-ion collisions, and argue the dependence of transverse momentum distributions and yields of exotic hadrons on their internal structures. Taking X(3872) and X(3915) mesons as examples, we not only discuss the centrality dependence of the yield on the internal structure of exotic hadrons in heavy ion collisions, but also investigate the dependence of the yield on the time when exotic hadrons are produced in heavy ion collisions. We propose, therefore, that heavy-ion collisions experiments offer an opportunity to gain a better understanding of heavy exotic hadrons, providing plausible answers to various fundamental problems in QCD.

Speaker: Sungtae Cho (Kangwon National University)

41 Femtoscopic study of pair correlations with nuclei

With the development of interaction femtoscopy, interactions in various flavor systems are being revolutionized and clarified. In particular, the interaction between strange particles and nucleons provides a foundation for a systematic understanding of hadron interactions. On the other hand, femtoscopy typically suffers from the drawback that it is difficult to decompose spin and isospin interaction components, as it can only provide data that are averaged over isospin and spin. To resolve this issue, this study discusses the utility and challenges of femtoscopy research using pairs of strange particles and nuclei.

Speaker: Prof. Yuki Kamiya (Tohoku University)

17:45 Workshop Banquet

Friday, 28 August

Session 11 - J-PARC experimental programme

42 Hadron Physics with Kaon Beams at the J-PARC K1.8BR and K1.8 Beam Lines

The K1.8BR and K1.8 beam lines at the J-PARC Hadron Experimental Facility provide intense secondary kaon beams in the momentum region of approximately 0.6–2 GeV/c, offering unique opportunities to study strange-hadron spectroscopy and hadron interactions. At K1.8BR, the E72 experiment investigates the $K^-p$ reaction near the $\Lambda\eta$ threshold to clarify the threshold enhancement and search for possible narrow $\Lambda\eta$ states using the large-acceptance HypTPC detector. At K1.8, higher-momentum kaon beams open further possibilities for studies of excited hyperons, multi-strangeness production, and meson–baryon dynamics. I will present the current status and future prospects of these kaon-beam programs.

Speaker: Prof. Shuhei Hayakawa (Tohoku University)

43 H-Dibaryon Search near the $\Lambda\Lambda$ and $\Xi^-p$ Thresholds at J-PARC

We report preliminary results from $\Lambda\Lambda$ invariant-mass spectroscopy in the $^{12}\mathrm{C}(K^-,K^+)$ reaction to search for the H-Dibaryon near the $\Lambda\Lambda$ and $\Xi^-p$ thresholds at J-PARC. The experiment employs a $1.8~\mathrm{GeV}/c$ $K^-$ beam incident on a diamond target and a large-acceptance hyperon spectrometer centered on a time-projection chamber (HypTPC). This setup provides sensitivity over a broad mass region, ranging from weakly bound states below the $\Lambda\Lambda$ threshold to possible structures above the $\Xi^-p$ threshold.

A total of approximately $3.0\times10^{5}$ $^{12}\mathrm{C}(K^-,K^+)X$ reaction events were collected, yielding several thousand $\Lambda\Lambda$ events-about two orders of magnitude more than in previous experiments. In the $(K^-,K^+)$ reaction on a nuclear target, $\Lambda\Lambda$ production proceeds through interactions on di-protons inside the nucleus. The production mechanisms include intermediate $\Xi^-$ formation as well as meson-induced two-step processes, such as
$K^-p \rightarrow \Xi^-K^+$ followed by $\Xi^-p \rightarrow \Lambda\Lambda$, and $K^-p \rightarrow \pi^0\Lambda$ followed by
$\pi^0p \rightarrow \Lambda K^+$.

In our earlier work, we measured the differential cross section for the $^{12}\mathrm{C}(K^-,K^+\Lambda\Lambda)$ reaction and separated the contributions from the $\Xi^-p \rightarrow \Lambda\Lambda$ conversion and meson-induced two-step processes~\cite{ref1}. Based on these results, we have carried out invariant-mass spectroscopy of the $\Lambda\Lambda$ system to investigate the possible existence of the H-Dibaryon near threshold and to gain further insight into the $\Lambda\Lambda$-$\Xi N$ interaction. In this presentation, we will show preliminary results of the H-Dibaryon search and discuss its nature.

Speaker: WooSeung Jung (JAEA)

44 Investigating the Λη Threshold Region with the J-PARC E72 Experiment

The Λη threshold region is of particular interest for understanding the excitation spectrum of Λ hyperons. Previous measurements of the K−p → Λη reaction revealed a strongly non-uniform angular distribution near threshold. Since a J/P = 1/2− resonance is expected to produce a nearly isotropic angular distribution in this region, the observed behavior cannot be readily explained by the established Λ(1670) resonance alone. This anomaly has been interpreted as a possible indication of an additional narrow Λ resonance close to the Λη threshold.
The J-PARC E72 experiment was designed to investigate this anomaly through a high-statistics measurement of the K−p → Λη reaction. The experiment employs the Hyperon Spectrometer, consisting of a superconducting dipole magnet and the Hyperon Time Projection Chamber (HypTPC), which provides large-acceptance tracking and precise momentum reconstruction of charged particles. The Λη final state is reconstructed by detecting the charged decay products from Λ → pπ− and identifying the η meson using the missing-mass technique.
The analysis presented here is based on the dataset collected during the November 2025 physics run with a K− beam momentum around 735 MeV/c, corresponding to the center-of-mass energy region near the Λη threshold. The collected dataset exceeds the statistics of previous measurements by approximately two orders of magnitude, enabling precise studies of differential cross sections and polarization observables. In this presentation, we will report the current status of the Λη event reconstruction, including Λ identification and missing-mass analysis, and discuss the expected sensitivity of E72 to a possible narrow Λ resonance near threshold.

Speaker: Haein Lee (Korea University)

10:15 Coffee Break

Session 12 - Hadron beams and baryon spectroscopy

45 Kaonic nuclear systems at J-PARC

Kaonic nuclei are exotic few-body systems in which an antikaon is bound as a constituent particle. They provide a unique testing ground for the strongly attractive subthreshold $\bar{K}N$ interaction and the resulting few-body dynamics. In the J-PARC E15 experiment, the simplest candidate, the ''$K^-pp$'' state, was observed as a structure in the $\Lambda p$ invariant-mass spectrum of the in-flight $K^-$ reaction on a helium-3 target, demonstrating the importance of complete kinematic reconstruction with a large-acceptance solenoid spectrometer.

We are now extending this program. With an upgraded solenoid spectrometer, J-PARC E80 will investigate the ''$K^-ppn$'' system using a helium-4 target, while E89 will determine the spin parity of ''$K^-pp$'' and search for its isospin partner, ''$\bar{K}^{0}nn$''. In parallel, we plan ultra-high-precision X-ray spectroscopy of light kaonic atoms, with particular emphasis on isotope differences, to provide precise constraints on the antikaon--nucleus interaction in the low-density nuclear surface region.
In this contribution, we review our achievements over the past decade and discuss future prospects for these complementary studies.

Speaker: Tadashi Hashimoto (RIKEN)

46 Spectroscopic study of the diquark correlation using hadron beams at J-PARC

Quantum Chromodynamics (QCD) has been firmly established as the fundamental theory of the strong interaction, and lattice QCD calculations have successfully bridged QCD and nuclear systems; however, the mechanism by which quarks build hadrons remains unresolved, particularly for excited states and exotic multiquark configurations that reflect the non-trivial dynamics of the low-energy QCD vacuum. Spin-dependent attractive interactions give rise to strong quark-pair correlations known as the diquark correlation, most prominently the scalar $0^+$ good diquark, which serve as crucial effective degrees of freedom not only in hadron spectroscopy and exotic structures, but also in dense hadronic matter and the color superconducting phase. To experimentally uncover these internal dynamics, systematic spectroscopic studies of charmed ($\Lambda_c$) and multistrange ($\Xi$,$\Omega$) baryons are proposed at J-PARC using high-momentum hadron beams. By exploiting excited states within diquarks composed of different flavor combinations ($u$,$d$,$s$), experiments at the $\pi 20$ ($\Lambda_c$,$\Xi$) and K10 ($\Omega$) beamlines aim to isolate these diquark degrees of freedom and firmly establish the diquark correlation which is essential for the hadron structure.

Speaker: Dr Kotaro Shirotori (Research Center for Nuclear Physics (RCNP), The University of Osaka)

47 Exploring N* and Delta* resonances in high-statistics pi N →pi pi N reactions at J-PARC E45

Nucleon resonances (N and Δ) have been studied for a long time mostly through
γN→πN. πN→πN, and γN→ππN reactions. However, there are many resonances which
have not been established experimentally, due to a limited number of πN→ππN reaction
data which was mainly measured in 1970’s. Thus, J-PARC E45 has been proposed to
study nucleon resonances in πN→ππN reactions with high-intensity π± beams injected on
the liquid hydrogen target at J-PARC. We aim to establish nucleon resonances with the
mass up to 2 GeV/c2 using πN→ππN reactions in higher statistics than the world’s existing
data by two-orders of magnitude. We will measure reactions of π−
p→π+π−
n, π0π−
p and
π+p→π0π+p, π+π+n, as well as π−
p→K0Λ and π+p→K+Σ+ in a large acceptance Time
Projection Chamber (HypTPC) inside a superconducting Helmholtz magnet. We will
measure these reactions in small momentum steps in the center-of-mass energy range of
1.5-2.1 GeV. Then, we perform partial wave analysis to extract properties of resonances.
The first physics run of E45 is planned in Nov. 2026 in the energy range of 1.66-1.75 GeV.
In this presentation, we will show the preliminary results of the commissioning run, and the
preparation status for the physics run.

Speaker: Prof. Hiroyuki Sako (JAEA)

12:00 Lunch

Session 13 - Electromagnetic processes and the instanton vacuum

48 Kaon Electromagnetic Production: A 70-Year Journey

Over the past seventy years, studies of the electromagnetic production of strangeness have evolved from pioneering photo- and electroproduction experiments into a powerful tool for investigating hadron structure and strong interactions. Early measurements established the foundation for understanding these reactions, while the continuous accumulation of experimental data stimulated the development of increasingly sophisticated theoretical frameworks, ranging from effective Lagrangian and isobar models to coupled-channel approaches, chiral perturbation theory, Regge models, and, more recently, lattice QCD. Together, these experimental and theoretical efforts have substantially improved our understanding of the underlying reaction mechanisms and the excitation spectrum of the nucleon.

A major breakthrough came in the 1990s with the advent of second-generation facilities such as ELSA, MAMI, SPring-8, and Jefferson Lab. High-intensity, high-duty-factor accelerators, together with advanced detector systems, modern electronics, and powerful computing resources, improved experimental capabilities by orders of magnitude compared with earlier generations. These advances greatly accelerated research in strangeness physics. To date, more than 50 dedicated kaon photo- and electroproduction experiments have been performed worldwide, providing a wealth of observables that have significantly deepened our understanding of strongly interacting systems involving the creation of an $s\bar{s}$ quark pair.

The resulting data have become an indispensable complement to other approaches for studying the spectrum and internal structure of excited nucleon states, including the search for missing and exotic baryons. They have also played a key role in investigations of hypernuclear production, providing valuable constraints on the hyperon--nucleon ($YN$) interaction, as well as in studies of the electromagnetic form factors of strange mesons.

This talk presents an overview of the experimental and theoretical developments in the electromagnetic production of strangeness over the past seven decades, based on our recent review published in Ref. [1]. It traces the evolution of both experimental techniques and theoretical descriptions, highlights the major milestones and current challenges in the field, and discusses future opportunities at next-generation experimental facilities.

Reference:

1. T. Mart, J. A. Djaja, D. Carman, Electromagnetic production of
   on the nucleon, Progress in Particle and Nuclear Physics 150,
   104252 (2026).

Speaker: Terry Mart (University of Indonesia)

49 Strange and Heavy Baryons in Nuclear Matter

We present a discussion of the mass spectrum of strange and heavy baryons in nuclear matter, based on the framework of the pion mean-field approach. We will also discuss possible applications of the approach to strangeness-mixed nuclear matter.

Speaker: Ulugbek Yakhshiev (Inha University)

50 Heavy exotic hadrons as molecular states

In recent years, there has been growing interest in exotic hadrons that exhibit structures beyond the conventional hadron picture, where baryons are treated as three-quark states ($qqq$) and mesons as quark--antiquark pairs ($q\bar{q}$). In the charm sector, many exotic hadrons such as $XYZ$, $P_c$, and $T_{cc}$ particles have been reported in experiments. Most of these states have appeared near hadron thresholds and hence have been considered as hadronic molecular states. However, the hadron--hadron interactions that is responsible for binding constituent hadrons are not yet fully understood. Understanding hadronic interactions is essential for uncovering the dynamics of low-energy QCD.

In this talk, we discuss hadronic molecules including heavy mesons (such as $D$ or $B$ mesons), focusing on their bound and resonant states using theoretical analysis. Heavy mesons are expected to be constituents of many hadronic molecular states, and thus understanding their interactions is very important to investigate the exotic hadrons. In the heavy hadron sector, the heavy quark symmetry is a key ingredient, which induces channel coupling effects and also predicts spin partner states. We study bound state properties of hadronic molecules of a heavy meson and a nucleon.

Speaker: Yasuhiro Yamaguchi (Tokyo Metropolitan University)

51 Heavy-Light Effective Theory in the QCD Instanton Vacuum

We develop a non-perturbative approach to heavy-quark effective theory based on the instanton-induced heavy-light effective action. The formalism incorporates spontaneous chiral symmetry breaking and heavy-quark spin symmetry from the outset and is reformulated in terms of chirally rotated constituent light quarks interacting with Goldstone bosons. Heavy-meson states emerge dynamically as collective excitations of light and heavy quarks, with their masses determined by quark-loop dynamics. The resulting framework provides a direct connection between the instanton vacuum and the low-energy description of heavy hadrons, allowing for a systematic evaluation of HQET observables. In particular, the residual mass parameter $\bar\Lambda$, the kinetic and chromomagnetic matrix elements, and higher-dimensional heavy-quark operator expectation values can be computed consistently within a unified effective field theory framework. Furthermore, the effective action provides a natural realization of local and nonlocal effective gluonic operators in heavy-light systems, enabling the study of quark-gluon correlations and the evaluation of matrix elements relevant for higher-order HQET and operator product expansion analyses. This approach opens a new avenue for investigating non-perturbative aspects of heavy-light hadrons directly from the underlying QCD vacuum structure.

Speaker: Dr Nurmukhammad Rakhimov (Inha University)

52 Heavy mesons from the QCD instanton vacuum

We investigate heavy mesons in the QCD instanton vacuum. The instanton-induced nonlocal four-quark interaction is bosonized in the heavy-light channel to derive an effective meson action. Using this action, we present a framework for calculating heavy-meson masses and decay constants, the kinetic and chromomagnetic matrix elements associated with (\lambda_1) and (\lambda_2), and the Isgur–Wise function.

Speaker: Ki-Hoon Hong

Closing