arXiv subjects

Bing-Song Zou

Publications and source records attributed to Bing-Song Zou.

At least 19 recordsLinked to original sources

arXiv2026

Charmed baryon semileptonic decays in a relativistic three-quark model

We study the spin-$1/2\to1/2$ semileptonic decays of singly charmed baryons ($\Lambda_c^+$, $\Xi_c^{0,+}$, and $\Omega_c^0$) into the light baryon octet within a relativistic three-quark model. The constituent quark masses and spatial wave functions are determined by the baryon mass spectrum. For the physical $\Xi_c$ states, the light flavor $\mathrm{SU}(3)$ breaking ($m_s > m_{u,d}$) naturally induces a coherent mixing between the flavor antitriplet and flavor sextet configurations, which is completely fixed by the mass eigenstates. Consequently, no adjustable parameters are introduced in calculating the weak transition amplitudes. Using these wave functions, we calculate the $c\to s,d$ helicity amplitudes with the Bakamjian--Thomas boost, including the spatial Jacobian and the Wigner rotations of the constituent spins. The branching fractions, $q^2$ distributions, longitudinal polarizations, and form factors are then obtained from these amplitudes. For the $\Lambda_c^+\to\Lambda\ell^+\nu_\ell$ and $\Lambda_c^+\to n\ell^+\nu_\ell$ modes, our branching fractions and form factors are in good agreement with the experimental data and Lattice QCD results. For $\Xi_c^0\to\Xi^-e^+\nu_e$, we obtain branch ratio $\mathcal B_{\ell} \simeq 4.0~\%$, which is consistent with recent Lattice QCD calculations but lies well above the current experimental average. Clarifying the origin of this discrepancy calls for further dedicated efforts from both experimental and theoretical sides. For the $\Omega_c^0\to\Xi^-\ell^+\nu_\ell$ decay, the spin-$1$ $ss$ spectator yields a positive longitudinal polarization of the final $\Xi^-$, in contrast to the negative polarizations in the predominantly antitriplet decay modes. Our predictions for the $q^2$ spectra, angular asymmetries, and final baryon polarizations may provide useful references for future measurements of singly charmed baryon semileptonic decays.

hep-ph↗

arXiv2026

On the Nature of $X(2370)$

Recently, the BESIII Collaboration claimed that their observed $X(2370)$ ($J^{PC}=0^{-+}$) is predominantly a glueball state based on several arguments. However, we find these arguments to be flawed and the conclusion unjustified. Instead, we demonstrate that all observed properties of the $X(2370)$ can be naturally explained by a $\bar\Sigma\Sigma$ molecule dominated state.

hep-ph↗

arXiv2026

Phase-constrained $\Sigma^*$ spectroscopy in the pure-$I=1$ reactions $K_Lp\to\pi^+\Sigma^0$ and $K_Lp\to\pi^+\Lambda$

Low-energy $\bar K N$ scattering provides direct access to strange-baryon spectroscopy, but conventional charged-kaon reactions mix the $I=0$ and $I=1$ amplitudes. Motivated by the isospin-selective nature of the $K_Lp$ reactions, we present, to our knowledge, the first simultaneous analysis of the pure-$I=1$ reactions $K_Lp\to\pi^+\Sigma^0$ and $K_Lp\to\pi^+\Lambda$ in which a common set of resonance parameters and a fixed relative-phase convention are imposed on both final states. Within an effective-Lagrangian model, a joint fit of available differential cross sections and recoil polarizations yields $\chi^2/\mathrm{d.o.f.}=1.604$. We find clear channel complementarity: the $t$-channel $K^*$ exchange is more important in $K_L p\to \pi^+\Lambda$, especially at forward angles, whereas $K_L p\to \pi^+\Sigma^0$ is more sensitive to the contribution of $\Sigma(1620)\,1/2^-$. At the same time, $\Sigma(1660)\,1/2^+$ remains important through interference effects in both channels. These results demonstrate the importance of multichannel, phase-constrained analyses for establishing the $I=1$ hyperon spectrum and provide timely phenomenological input for future high-precision measurements by the KLF program at JLab. Once the pure $I=1$ amplitudes are reliably determined, they will also enable the separation of the $I=0$ component in the much more abundant $K^- p\to \pi^\pm\Sigma^\mp$ data, opening a path toward a more quantitative study of the $\Lambda^*$ spectrum.

hep-ph↗

arXiv2026

Radiative corrections in neutral-current (anti)neutrino elastic scattering at $\text{GeV}$ energies I: Nucleon targets

We introduce radiative corrections in neutral-current (anti)neutrino-nucleon elastic scattering at $\text{GeV}$ energies within the effective field theory framework. We factorize cross sections into soft and hard functions, clarify the (anti)neutrino flavor dependence at both amplitude and cross-section levels, and improve the quantum chromodynamics (QCD) contributions to low-energy neutral-current processes. The radiative corrections at the single-nucleon level reach a magnitude comparable to the contributions from strange quarks. We also compare our results with the experimental data from BNL E734 and MiniBooNE collaborations, finding excellent agreements with the experimental data.

hep-ph↗

arXiv2026

Exploring $K\Xi^$ and $K^\Xi$ molecular states and the triangle singularity in the $K^- p \to K \Xi(1530)$ reaction

We investigate the $K^- p \to K \Xi(1530)$ reaction within an effective Lagrangian approach, exploring possible $K \Xi^*$ and $K^* \Xi$ hadronic molecular states and the role of the triangle singularity (TS). The $\Lambda(2050)3/2^-$ is interpreted as a $K \Xi^*$ molecule, whereas a $K^* \Xi$ molecule with $I(J^P)=0(3/2^-)$ and mass about 2150~MeV denoted as $\Lambda(2150)$ can generate a TS through triangle-loop diagrams with intermediate $K^*$, $\Xi$, and $\pi$. The peak structure observed in the cross section near $\sqrt{s}=2.25$ GeV is analyzed in terms of both the $\Sigma(2250)$ resonance production and the TS mechanism associated with $\Lambda(2150)$. We find that the TS induces pronounced spin effects in the final state $\Xi^*$, which can be probed through measurements of its spin density matrix elements. In particular, significant variations of the spin observables in the $\sqrt{s}=2.2$--$2.3$ GeV region serve as a distinct TS signature absent in a pure resonance scenario. Furthermore, for the three-body reaction $K^- p \to K^+ \pi^- \Xi^0$, we demonstrate that $\Xi^*$ spin observables can be reliably extracted from the $\pi$ angular distribution in the $\Xi \pi$ rest frame by applying an appropriate kinematic cut on the $\Xi\pi$ invariant mass to suppress background contributions. These predictions can be tested in future high-precision measurements at J-PARC, providing crucial insights into the nature of the TS and the possible existence of the $K^* \Xi$ molecular state.

hep-ph↗

arXiv2026

Unified study of hyperon semileptonic decays in a relativistic three-quark model

We present a unified theoretical study of semileptonic decays of ground state octet hyperons using the relativistic three-quark model (R3QM). A key innovation of our approach is that all baryon wave functions are determined by fitting the baryon mass spectrum with a semirelativistic potential model, leading to predictions for weak transition amplitudes without free parameters. Adopting these wave functions, we calculate the decay widths, branching fractions, lepton flavor universality ratios, as well as the angular correlation and spin asymmetry parameters for the octet channels. The calculated values agree with the available experimental data and give predictions for channels with limited experimental information. We further compute the complete set of octet transition form factors without any additional free parameters, so that the weak current can be examined beyond the rate observables. In the well measured $\Lambda \to p \ell^-\bar{\nu}_\ell$ channel, the calculated leading vector and axial-vector form factors, $f_1(0)$ and $g_1(0)$, agree well with recent lattice QCD results, and the $g_1/f_1$ ratio is consistent with recent BESIII measurements. Beyond the leading vector and axial-vector terms, the complete form factor set separates the weak magnetism, second class, and the pole contribution associated with the partially conserved axial current (PCAC) relation. The weak magnetism term $f_2$ shows the clearest channel dependence compared with lattice QCD results, and its smaller values in some channels may point to transverse current strength not fully saturated by pure $qqq$ valence components. This work provides a framework for connecting octet hyperon weak form factors to the spin--flavor and spatial structure of baryons at the quark level, and gives testable weak current observables for future hyperon semileptonic decay measurements.

hep-ph↗

arXiv2026

A possible $\Sigma^$ or $\Lambda^$ resonance with $J^P=3/2^-$ in $K^-p\to K\Xi$ scattering

We analyze the $K^-p\to K^+\Xi^-$ and $K^-p\to K^0\Xi^0$ processes in the energy region $1.8<\sqrt{s}<2.8$ GeV within an effective Lagrangian approach. The $\Lambda(1800)$ and $\Sigma(2250)$ resonances, along with the ground states $\Sigma$ and $\Lambda$, are included. Additionally, a possible $J^P=3/2^-$ $\Sigma^*$ or $\Lambda^*$ resonance with a mass around 1.9 GeV and a width of approximately 200 MeV is introduced to describe the structure at 2.0 GeV in the total cross section and reproducing the threshold behavior. The two possible solutions corresponding to $\Sigma^*(3/2^-)$ and $\Lambda^*(3/2^-)$ cannot be distinguished by the existing data. Predictions for the polarization of the final-state $\Xi$ and the cross section of $K^-n \to K^0\Xi^-$ are compared with the experimental data, we find that the results of solution-II with $\Lambda^*(3/2^-)$ are much better. We also discuss the possible interpretations of the introduced $3/2^-$ hyperon as a pentaquark candidate, e.g. an $S$-wave $K\Xi(1530)$ hadronic molecule. However, since the polarization data suffer from rather large uncertainties, more data inputs are needed in future experiments, for example, J-PARC, HIAF and JLab.

hep-ph↗

arXiv2026

Study of the decay pattern of $f_0 (1370)$ as a $\kappa \bar{\kappa }$ molecular state

Under the hypothesis that the $f_0(1370)$ is a $\kappa \bar{\kappa}$ molecular state, we calculate the partial widths of its various decay channels, including the two-body decay $K \bar{K}$, $\pi \pi$, $\eta \eta$ and the four-body decay $\rho \rho / \sigma \sigma \to 4 \pi$ and $K \bar{K} \pi \pi$. The coupling of $g_{f_0(1370) \kappa \bar{\kappa}}\approx 13$ GeV estimated from the Weinberg criterion yields a width of $f_0(1370)$ significantly smaller than the experimental data. By adjusting this coupling to $25 \sim 40$ GeV, the total width of $f_0(1370)$ can be fitted to the measured value $200\sim 500$ MeV. At the center-of-mass energy $\sqrt{s}=1.37$ GeV, the channels that mainly contribute to the total width are $K \bar{K}$, $\pi \pi$ and $4 \pi$ ranked as $\Gamma(K \bar{K }) > \Gamma(4 \pi) \approx \Gamma (\pi \pi) $ with $g_{f_0(1370) \kappa \bar{\kappa}}= 35$ GeV. Around $1.37$ GeV, the decay widths of the two-body channels $K \bar{K}$, $\pi \pi$ and $\eta \eta$ remain stable with variation in $\sqrt{s}$, whereas the decay widths of the four-body channels $4 \pi$ and $K \bar{K }\pi \pi$ increase continuously with $\sqrt{s}$. Most current data are model-dependent and conflicting, particularly regarding the conclusion of $4 \pi$ dominance and the ratio of $K\bar{K}$ to $\pi \pi$ decay widths. The current data can not rule out the $\kappa \bar{\kappa}$ assignment for $f_0(1370)$. Further reliable theoretical and experimental analyses of $f_0(1370)$ are required to reveal its nature.

hep-ph↗

arXiv2026

Charmonium, exotic hadrons and hadron structure

To celebrate the 50th anniversary of the discovery of the J/{\psi}, the first charmonium state observed, I start with a brief review of major progresses on the QCD inspired quark potential model originated from charmonium spectrum.Then I show the importance of unquenching dynamics, multiquark components and exotic multiquark states for understanding hadron structure and hadron spectrscopy. The J/{\psi} and charmonium-like states have played an important role in this aspect.

hep-ph↗

arXiv2025

Huizhou Hadron Spectrometer -- a Proposed High-rate Experimental Setup at the High Intensity Heavy-ion Accelerator Facility

The High-Intensity Heavy-Ion Accelerator Facility (HIAF), currently under construction in Huizhou, Guangdong Province, China, is projected to be completed by 2025. This facility will be capable of producing proton and heavy-ion beams with energies reaching several GeV, thereby offering a versatile platform for advanced fundamental physics research. Key scientific objectives include exploring physics beyond the Standard Model through the search for novel particles and interactions, testing fundamental symmetries, investigating exotic hadronic states such as di-baryons, pentaquark states and multi-strange hypernuclei, conducting precise measurements of hadron and hypernucleus properties, and probing the phase boundary and critical point of nuclear matter. To facilitate these investigations, we propose the development of a dedicated experimental apparatus at HIAF - the Huizhou Hadron Spectrometer (HHaS). This paper presents the conceptual design of HHaS, comprising a solenoid magnet, a five-dimensional silicon pixel tracker, a Low-Gain Avalanche Detector (LGAD) for time-of-flight measurements, and a Cherenkov-scintillation dual-readout electromagnetic calorimeter. The design anticipates an unprecedented event rate of 1-100 MHz, extensive particle acceptance, a track momentum resolution at 1% level, an electromagnetic energy resolution of ~3% @ 1 GeV and multi-particle identification capabilities. Such capabilities position HHaS as a powerful instrument for advancing experimental studies in particle and nuclear physics. The successful realization of HHaS is expected to significantly bolster the development of medium- and high-energy physics research within China.

hep-ex↗

arXiv2025

$ϕ$ and $J/ψ$ Production in Proton-Proton Scattering through Hadronic Molecules

This study estimates the contributions of hidden-strangeness hadronic molecular states ($N(2080)3/2^-$, $N(2270)3/2^-$) to $ϕ$ production and hidden-charm $P_c$ states to $J/ψ$ production in $pp$ collisions. The calculated cross-sections reach $\sim 10~μb$ for $pp\to ppϕ$ and $\sim 0.1~nb$ for $pp\to pp J/ψ$ at energies $\sim 2$~GeV above threshold. We also compute the spin density matrix element $ρ_{00}$ and the decay angular distributions for $ϕ\to K^+K^-$ and $J/ψ\toμ^+μ^-$. To support future experiments, we conduct Monte Carlo simulations for the four-body final states of $pp\to ppK^+K^-$ and $pp\to ppμ^+μ^-$. The resulting lab-frame distributions are expected to inform detector design at facilities like the High-Intensity heavy-ion Accelerator Facility (HIAF) and the proposed Chinese Advanced Nuclear Physics Research Facility (CNUF), enabling more precise measurements and tighter theoretical constraints. Furthermore, to explain the STAR collaboration's result on $ϕ$ meson spin alignment in heavy-ion collisions, we propose a novel mechanism involving hidden-strangeness molecular states, testable with future high-statistics $pp\to ppϕ$ data.

hep-ph↗

arXiv2025

Effects of strange molecular partners of $P_c$ states in $γp \to K Σ$ reactions

Our previous studies revealed evidence of the strange molecular partners of $P_c$ states, $N(2080)3/2^-$ and $N(2270)3/2^-$, in the $γp \to K^{*+} Σ^0 / K^{*0} Σ^+$ and $γp \to ϕp$ reactions. Motivated by the differential cross-section data for $γp \to K^+ Σ^0$ from CLAS 2010, which exhibits some bump structures at $W \approx$ 1875, 2080 and 2270 MeV, we extend our previous analysis by investigating the effects of $N(1535)1/2^-$, $N(1875)3/2^-$, $N(2080)1/2^- \&\ 3/2^-$ and $N(2270)1/2^- , 3/2^- \&\ 5/2^-$, as strange partners of $P_c$ molecular states, in the reactions $γp \to K^+ Σ^0$ and $γp \to K^0 Σ^+$. The theoretical model employed in this study utilizes an effective Lagrangian approach in the tree-level Born approximation. It contains the contributions from $s$-channel with exchanges of $N$, $Δ$, $N^*$ (including the hadronic molecules with hidden strangeness), and $Δ^*$; $t$-channel; $u$-channel; and the generalized contact term. The results based on the final fitted parameters are in good agreement with all available experimental data of both cross-sections and polarization observables for $γp \to K^+ Σ^0$ and $γp \to K^0 Σ^+$. Notably, the $s$-channel exchanges of molecules significantly contribute to the bump structures in cross-sections for $γp \to K Σ$ at $W \approx$ 1900, 2080 and 2270 MeV, and show considerable coherence with contributions from $s$-channel exchanges of general resonances to construct the overall structures of cross-sections. More abundant experiments, particularly for the reaction $γp \to K^0 Σ^+$, are necessary to further strengthen the constraints on the theoretical models.

nucl-th↗

arXiv2025

Nature of the $P_c$ states from compositeness criteria

Based on a coupled-channel approach, we investigate the structures of four $P_c$ states through compositeness criteria. Toward a more precise description of the states, we have obtained refined fit results of the LHCb data on the $J/ψp$ invariant mass distribution of the $Λ_b^0\to J/ψp K^-$ decay. Allowing for the fact that each of the four $P_c$ states couples strongly to a nearby $S$-wave channel, three criteria on the compositeness/elementariness are adopted in this study: the pole-counting rule, the spectral density function, and the Gamow wave function. Compositeness information is extracted from the scattering amplitudes and the pole parameters (pole positions and residues), without any preconceived assumptions on the nature of the $P_c$ states, and without any dependence on the model parametrization. Consistently within the framework of all the three methods, it has been found that the $P_c(4312)\,1/2^-$ is mainly composed by $\bar{D}Σ_c$, $P_c(4380)\,3/2^-$ by $\bar{D}Σ_c^*$, while the $P_c(4440)\,1/2^-$ and $P_c(4457)\,3/2^-$ states both turn out as composite states of $\bar{D}^*Σ_c$. The upper limits of the values of their elementariness are estimated to be rather small. This paper provides an additional confirmation of the molecular interpretation for the $P_c$ states in the literature.

hep-ph↗

arXiv2025

Effects of hadronic molecule $N(2080)3/2^-$ on $K^{*+}Λ$ photoproduction

In our previous work [Phys. Rev. C {\bf 101}, 014003 (2020)], we have analyzed all available data on differential cross sections and spin density matrix elements for the $γp \to K^{\ast +} Λ$ reaction using an effective Lagrangian approach. There, the $t$-channel $K$, $K^*$, and $κ$ exchanges, the $u$-channel $Λ$, $Σ$, and $Σ^*$ exchanges, the $s$-channel $N$, $N(2060)5/2^-$, and $N(2000)5/2^+$ exchanges, and the interaction current were taken into account in constructing the reaction amplitudes. It was found that, overall, the agreement of the theoretical results with the corresponding data is fairly good. However, noticeable discrepancies between the model results and the data on spin density matrix elements $ρ_{00}$ are still observed in the center-of-mass energy region around $W \approx 2.08$ GeV, indicating the need for additional reaction mechanisms. On the other hand, the hidden-strange pentaquark-like state $N(2080)3/2^-$, which is proposed to be a $K^*Σ$ molecular state as the strange partner of $P_c(4457)$ hadronic molecule, has been found to play quite active roles in reproducing the data for $K^{*+}Σ^0$, $K^{*0}Σ^+$, and $ϕp$ photoproduction reactions. Based on these observations, in the present work, we reanalyze the data for the $γp \to K^{\ast +} Λ$ reaction by incorporating the pentaquark-like state $N(2080)3/2^-$ in our previously proposed model. The results show that with the inclusion of the contributions of $N(2080)3/2^-$, the quality of the theoretical description of the $γp \to K^{*+}Λ$ data can be considerably improved.

hep-ph↗

arXiv2025

Roper resonance $N^*(1440)$ from charmonium decays

The Roper resonance $N^*(1440)$ was discovered by David Roper in 1964 through sophisticated partial-wave analyses of $πN$ scattering data. However the first direct observation of the Roper resonance peak in the $πN$ invariant mass spectrum was only realized 40 years later from the charmonium decay $J/ψ\to\bar pnπ^+ +c.c.$ at Beijing Electron-Positron Collider. The further observations of the Roper resonance production from various charmonium decays helped to reveal its multiquark nature with large $σN$ component.

hep-ph↗

arXiv2025

Two-photon production of $f_0$ and $a_0$ resonances as hadronic molecules composed of two vector mesons

Ascribed as $ρρ$ and $K^* \bar{K}^*$ molecular states, respectively, iso-scalar $f_0(1500)$ and $f_0(1710)$ states are expected to have iso-vector partners, potentially identified as $a_0(1450)$ and $a_0(1710)$. The predicted dominant decay modes for these two $a_0$ resonances are $a_0(1450) \to ωππ$ and $a_0(1710) \to ωππ,\,ϕππ$. We estimate cross sections for two-photon production of these four resonances within the hadronic molecular picture, and demonstrate that SuperKEKB's luminosity is sufficient for their observation and more precise parameter measurements.

hep-ph↗

arXiv2025

Analysis of $Σ^*$ via isospin selective reaction $K_Lp \to π^+Σ^0$

The isospin-selective reaction $K_Lp \to π^+Σ^0$ provides a clean probe for investigating $I=1$ $Σ^*$ resonances. In this work, we perform an analysis of this reaction using an effective Lagrangian approach for the first time, incorporating the well-established $Σ(1189) 1/2^+$, $Σ(1385) 3/2^+$, $Σ(1670) 3/2^-$, $Σ(1775) 5/2^-$ states, while also exploring contributions from other unestablished states. By fitting the available differential cross section and recoil polarization data, adhering to partial-wave phase conventions same as PDG, we find that besides the established resonances, contributions from $Σ(1660) 1/2^+$, $Σ(1580) 3/2^-$ and a $Σ^*(1/2^-)$ improve the description. Notably, a $Σ^*(1/2^-)$ resonance with mass around 1.54 GeV, consistent with $Σ(1620)1/2^-$, is found to be essential for describing the data in this channel, a stronger indication than found in previous analyses focusing on $πΛ$ final states. While providing complementary support for $Σ(1660) 1/2^+$ and $Σ(1580) 3/2^-$, our results highlight the importance of the $Σ(1620) 1/2^-$ region in $K_Lp \to π^+Σ^0$. Future high-precision measurements are needed to solidify these findings and further constrain the $Σ^*$ spectrum.

hep-ph↗

arXiv2025

Study of nucleon and $Δ$ resonances from a systematic analysis of $K^\astΣ$ photoproduction

A systematic analysis of the $K^\astΣ$ photoproduction off proton is performed with all the available differential cross section data. We carry out a strategy different from the previous studies of these reactions, where, instead of fixing the parameters of the added resonances from PDG or pentaquark models, we add the resonance with a specific $J^P$ and leave its parameters to be determined from the experimental data. When adding only one resonance, the best result is to add one $N(3/2^-)$ resonance around $2097$ MeV, which substantially reduces the $χ^2$ per degree of freedom to $1.35$. There are two best solutions when adding two resonances, one is to add one $N^\ast(3/2^-)$ and one $N^\ast(7/2^-)$, the other is to add one $N^\ast(3/2^-)$ and one $Δ^\ast(7/2^-)$, leading the $χ^2$ per degree of freedom to be $1.10$ and $1.09$, respectively. The mass values of the $N^\ast(3/2^-)$ in the two resonance solutions are both near $2070$ MeV. Our solutions indicate that the $N(3/2^-)$ resonance around $2080$ MeV is strongly coupled with the $K^\astΣ$ final state and support the molecular picture of $N(2080, 3/2^-)$.

hep-ph↗