The 23rd International Conference on Few-Body Problems in Physics (FB23)

This talk will present three recent studies conducted using data samples collected by the BESIII detector at center-of-mass energies ranging from 3.51 to 4.95 GeV. The investigations encompass hidden-charm, open-charm, and baryon final states. Specifically, the studies include the following: 1) Investigation of e+ e- -> K+ K- psi(2S), measuring the Born cross-sections and searching for new...

Since 2003, many hadrons that do not fit into the conventional quark model of qqbar mesons and qqq baryons have been discovered experimentally. Because most (if not all) of these states are located to the thresholds of pair of conventional hadrons, they have been conjectured to be hadronic molecules. There have been extensive theoretical and experimental studies to verify or refute the...

With the description that for a pure molecule state the effective range $r_0$ should satisfy the condition of $r_0 > 0$ and the fact that $r_0$ could be matched with the couplings related to momentum term in contact field theory, we can fit the low energy couplings up to NLO in the contact effective theory describing the 3 $P_c$ pentaquarks observed by LHCb in 2019 and finally get the...

Whether the $N\bar{N}$ interaction could form a state or not is a long standing question, even before the observation of the $p\bar{p}$ threshold enhancement in 2003. The recent high statistic measurement in the $J/\psi \to \gamma 3(\pi^+\pi^-)$ channel would provide a good opportunity to probe the nature of the peak structures around the $p\bar{p}$ threshold in various processes. By...

The strong attractive interaction of the ϕ meson and the proton is reported by ALICE collaboration recently. The corresponding scattering length is given as Re(f0)=0.85±0.34(stat)±0.14(syst)fm and Im(f0)=0.16±0.10(stat)±0.09(syst)fm. The fact that the real part is significant in contrast to the imaginary part indicates a dominate role of the elastic scattering, whereas the inelastic process is...

Currently, the $DD^{\ast}$, $D\bar{K}$ and $D^{\ast}\bar{K}$ systems are studied from both theoretical and experimental sides. The three hadronic molecules $T_{cc}^+$, $D^\ast_{s0}(2317)$ and $D_{s1}(2460)$ are found in the above three two-body systems. We consider chiral effective field theory, get the interactions of $DD^{\ast}$, $D\bar{K}$, $D^{\ast}\bar{K}$ systems on lattice, find a...

We present the determination of the charm quark mass, the masses and decay constants of charmed mesons using thirteen 2+1 flavor full-QCD gauge ensembles at five different lattice spacings $a\in[0.05,0.11]$ fm, 8 pion masses $m_{\pi}\in(130,360)$ MeV, and several values of the strange quark mass, which facilitate us to do the chiral and continuum extrapolation. These ensembles are generated...

At BESIII, the R value is measured with the corresponding c.m. energy going from 2.2324 to 3.6710 GeV by measuring the inclusive hadronic cross section. An accuracy of better than 2.6% below 3.1 GeV and 3.0% above is achieved in the R values. Besides, the measurements of normalized differential cross sections of inclusive hadrons as a function of hadron momentum are performed at BESIII, for...

We propose a novel method to probe light-quark dipole moments by examining the azimuthal asymmetries between a collinear pair of hadrons in semi-inclusive deep inelastic lepton scattering off an unpolarized proton target at the Electron-Ion Collider. These asymmetries provide a means to observe transversely polarized quarks, which arise exclusively from the interference between the dipole and...

The BESIII experiment has collected 10 billion J/psi events, 2.6 billion psi(3686) events, and about 20 fb^-1 psi(3770) data. Various dark sectors produced in e+e- annihilation and hadron decay processes can be searched for at BESIII. In this talk, we report the search for invisible dark photon decay using initial state radiation, invisible muonic Z’ boson decay, sigma invisible decay, and...

In this talk, we will introduce a new color basis system and confinement mechanism for multi-quark systems within QCD’s string-like framework. This approach extends the color Hilbert space for $QQ\bar{Q}\bar{Q}$ states to include a "hidden color" state that mixes with two-meson states, leading to an attractive potential sufficient for bound state formation. Using a realistic Hamiltonian model,...

In this talk, I will discuss recent progress towards achieving self-consistency in the light-front quark model. Typically, observables are computed using the good (or plus) current; however, computations using other currents, such as the transverse or minus current, often suffer from inconsistencies, resulting in different values. Self-consistency can be achieved in the standard light-front...

We propose a chiral quark model that incorporates vector mesons and apply it to the study of the hadron spectrum. We consider the contributions of vector mesons within the framework of hidden local symmetry. Our results demonstrate a significant improvement in the masses of ground state baryons, including the nucleon, $\Lambda_c$, and $\Lambda_b$. We successfully reproduce the masses of all 45...

The observation of the $T_{c\bar{s}}(2900)$ indicates the potential existence of strange double charm pentaquarks based on the heavy antidiquark symmetry. We systematically study the mass spectra of strange double charm pentaquarks with strangeness $S=-1$ in both molecular and compact structures for quantum numbers $J^{P}=1/2^{-}$, $3/2^{-}$, $5/2^{-}$. By constructing the interpolating...

Since the discovery of the $\chi_{c1}(3872)$ (aka $X(3872)$) state, many states compatible with tetraquarks have been observed, and many theoretical models have been proposed to explain these observations. However, there is still no consensus on the nature of tetraquark states. Further experimental studies of tetraquark states will help to test the theoretical model.
The LHCb experiment, with...

Scattering amplitudes involving three-particle scattering processes are investigated within the isobar approximation which respects constraints from two- and three-body unitarity. The particular system considered is the $D^0D^{*+}-D^+D^{*0}$, where the $D^{*+}$~$(D^{*0})$ enters as a $p$-wave $D^+\pi^0$ or $D^0\pi^+$~($D^0\pi^0$ or $D^+\pi^-$) resonance. The interaction potentials in the...

The Schrodinger equation with a Yukawa type of potential is solved analytically. When different boundary conditions are taken into account, a series of solutions are indicated as Bessel function, the first kind of Hankel function and the second kind of Hankel function, respectively. Subsequently, the scattering processes of $K \bar{K}^*$ and $D \bar{D}^*$ are investigated. In the $K \bar{K}^*$...

This talk is based on [Eur.Phys.J.C 84 (2024) 8, 800]. A novel approach is proposed to probe the nature of the double charm tetraquark through the prompt production asymmetry between $T_{\bar{c}\bar{c}}^-$ and $T_{cc}^+$ in pp collisions. When comparing the compact tetraquark picture and hadronic molecular picture, we find that the former one exhibits a significantly larger production...

Properties of near-threshold exotic hadrons in the spectrum of heavy quarks are sensitive to multi-body effects that are particularly relevant for states containing charmed quarks. I will discuss few-body effects in heavy flavour hadronic molecules at the example of the tetraquark Tcc+ state discovered recently by the LHCb collaboration and studied on the lattice.

We study the decays $\bar B^0 \to \bar K^0 \, X$, $B^- \to K^- \, X$, $\bar B^0_s \to \eta (\eta')\, X$, $\bar B^0 \to \bar K^{*0} \, X$, $B^- \to K^{*-} \, X$ , $\bar B_s^0 \to \phi \, X$, with $X \equiv X(3872)$, from the perspective of the $X(3872)$ being a molecular state made from the interaction of the $D^{*+} D^-, D^{*0} \bar D^0$ and $c.c.$ components. We consider both the external and...

The work of Eur. Phys. J. C 83 (2023) 983 will be presented, in which we perform a fit to the LHCb data on the $T_{cc}(3875)$ state in order to determine its nature. We use a general framework that allows to have the $D^0 D^{*+}$, $D^+ D^{*0}$ components forming a molecular state, as well as a possible nonmolecular state or contributions from missing coupled channels.

This talk is based on [Phys.Rev.D 110 (2024) 1, 014001]. Recently entanglement suppression was proposed to be one possible origin of emergent symmetries. Here we test this conjecture in the context of heavy meson scatterings. The low-energy interactions of $D^{(*)}\bar D^{(*)}$ and $D^{(*)} D^{(*)}$ are closely related to the hadronic molecular candidates $X(3872)$ and $T_{cc}(3875)^+$,...

The proposed STCF is a symmetric electron-positron beam collider designed to provide e+e− interactions at a centerof-mass energy from 2.0 to 7.0 GeV. The peaking luminosity is expected to be 0.5×10^35 cm−2s−1. STCF is expected to deliver more than 1 ab−1 of integrated luminosity per year. The huge samples could be used to make precision measurements of the properties of XYZ particles; search...

The study of light hadron decays has yielded significant insights into the fundamental properties of matter and the strong interactions between quarks. With the unprecedented statistics of 10 billion J/psi events collected with the BESIII detector, a wide range of processes involving light hadrons, including both light meson and hyperons, were explored for the new decay modes, new mechanisms...

Hadron spectroscopy studies can provide insights into the internal structure and dynamics of hadrons, thus improving our knowledge of the non-perturbative regime of QCD. The large b- and c-hadron yields at LHCb and the good performance of the LHCb detector make it an excellent laboratory for such studies, providing unique opportunities for both the precise measurement of properties of...

The LHCb experiment collected the world's largest sample of charmed hadrons in proton-proton collisions during LHC Run 1 and Run 2. With this data set, LHCb is offering an unprecedented opportunity to enhance our understanding of these particles through searching for new decay channels [1], measurement of b-baryon properties [2], measurement of the mass and production [3]. This presentation...

Studies of pentaquark states can improve our understanding of the strong interaction at the low-energy region. In 2015, the first candidates for pentaquark states were observed at LHCb. Since then, significant experimental and theoretical efforts have focused on pentaquark research. However, the internal structure and dynamics of tetraquarks remain a topic of active debate, calling for more...

In our work, we dynamically generate the bound states with the chiral unitary approach with the coupled channels, and evaluate the correlation functions for each channel. Then we address the inverse problem starting from these correlation functions to determine the scattering observables related to the system, including the existence of the bound state and its molecular nature. Assuming the...

Femtoscopic correlations with the $π^0π^0$ pair are measured in photoprodution at $E_{\gamma}$=1.3−2.4 GeV to extract the space-time geometry of the pion emission region. The $π^0π^0$ photoprodution experiment was carried out at Spring-8 BL31LEP with a linearly polarized photon beam using a 4π electromagnetic calorimeter BGOegg. Enhancement due to quantum statistics arising from Bose-Einstein...

We investigate the nucleon self energy through the sixth chiral order in the covariant SU(2) chiral perturbation theory (χPT) in the single baryon sector using the extended-mass-on-shell(EOMS) scheme. It is found that the EOMS scheme exhibits quite satisfactory convergence behavior through O(q^6) around physical point. We also predict the pion mass dependence of the nucleon mass to the...

Scattering reactions can be used to study the properties of hadron resonances. The traditional analysis method is to fit experimental data by adjusting the quantum number and parameters of the resonance. I would introduce a new method, which is the application of neural networks (NN), to study hadron resonances. The advantage of the NN method is that it can give quantitative probabilities in...

We will demonstrate the physical significance of the study of the semileptonic decay. The various theoretical tools such as the quark model will be explained.
We will dispay our prediction for several observables that can be tested in experiment.

The validity range of the time-honored effective range expansion can be very limited due to the presence of a left-hand cut close to the two-particle threshold. Such a left-hand cut arises in the two-particle interaction involving a light particle exchange with a mass small or slightly heavier than the mass difference of the two particles, a scenario encountered in a wide range of systems....

Motivated by the recent BESIII report on $J/\psi\rightarrow\gamma K^S_0K^S_0\pi^0$ decay, we firstly perform a disperisve analysis to study the final-state-interactions (FSIs) in the three-body unitarity and try to gain some insights into the nature of long-standing puzzles of isos-scalar pseudo-scalar $\eta(1405/1475)$ which is related the radially excited states of $\eta-\eta'$ and...

Charmed hadron decays offer an excellent environment for studying non-perturbative QCD. In addition, these decays involving scalar and vector mesons as final state particles play a crucial role in investigating the nature of scalar mesons, like a0 and f0, as well as examining the decay of vector mesons, like phi.

The BESIII experiment has collected 7.33 fb^-1 and 20 fb^-1 at 4.128-4.226 GeV...

We propose a novel method to identify the two-pole structure of the $\Lambda(1405)$. The two poles owe their origin to different quark flavor irreducible representations in the meson-baryon coupled-channel interactions, thus they should be individually manifested in reactions that provide good flavor eigenstate sources. Hadronic decays of charmonia into $\bar{\Lambda}\Sigma\pi$ and...

an introduction of EicC