arXiv subjects

Bing-Song Zou

Publications and source records attributed to Bing-Song Zou.

At least 37 records · Page 2Linked to original sources

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↗

arXiv2025

Evidence for the existence of a flavor-sextet charmed meson?

Recently, the LHCb Collaboration reported a signal for a new resonance in the $D_s^+ π^\pm$ invariant mass distribution in the decays $B\to \bar{D}^{(*)} D_s^+ π^+ π^-$ (arXiv:2411.03399). This could be a direct observation of an SU(3) flavor-sextet charmed meson with $J^P=0^+$. Such an SU(3) multiplet, is beyond the conventional quark-antiquark picture, and thus a verification of this observation is important.

hep-ph↗

arXiv2025

Two-pole structures in QCD -- a universal phenomenon governed by chiral dynamics

We illustrate how the two-pole structures of the $Λ(1405)$ emerge from the underlying universal chiral dynamics that describe the coupled-channel interactions between octet baryons and pseudo-Nambu-Goldstone bosons. Specifically, we attribute this phenomenon to the form of the leading-order chiral potential, which is of the Weinberg-Tomozawa type. We reveal how the underlying chiral dynamics can be exposed by examining the light-quark mass evolution of the two poles. The latest lattice QCD simulations have indeed found evidence for the existence of the two poles of $Λ(1405)$, in qualitative agreement with our predictions. We briefly mention a recent work in which lattice QCD simulations are studied more quantitatively, along with a proposal for how the SU(3) flavor content of the two poles of $Λ(1405)$ can be experimentally verified.

hep-ph↗

arXiv2025

The $J/ψ$-nucleon interaction mechanism: A theoretical study based on scattering length

The low-energy $J/ψN$ scattering is of significant importance for various reasons. It is deeply interconnected with the hidden-charm $P_c$ pentaquark states, provides insights into the role of gluons in nucleon structures, and is pertinent to the properties of $J/ψ$ in nuclear medium. The scattering can occur through two distinct mechanisms: the coupled-channel mechanism involving open-charm meson-baryon intermediate states $Λ_c \bar D^{(*)}$ and $ Σ_c^{(*)}\bar D^{(*)}$, and the soft-gluon exchange mechanism. In this study, we investigate the $S$-wave $J/ψN$ scattering length arising from both mechanisms. Our findings indicate that both mechanisms lead to attractive interactions, yielding scattering lengths of $[-10, -0.1] \times 10^{-3}$ fm for the coupled-channel mechanism and $<-0.16$ fm for the soft-gluon exchange mechanism, respectively. Notably, the soft-gluon exchange mechanism produces a scattering length that is at least one order of magnitude larger than that from the coupled-channel mechanism, indicating its predominance. These findings can be corroborated through lattice calculations and will enhance our understanding of scattering processes that violate the Okubo-Zweig-Iizuka rule.

hep-ph↗

arXiv2025

Establishing the vector-meson-exchange dominance for the short range interactions of light quarks

I give a brief comment on a recent study revealing the vector meson exchange (VME) dominant for the short range interactions between u/d quarks in the $NN$, $D_{03}$, and $D_{30}$ systems. The finding echoes nicely with an earlier study of hadron spectroscopy using a quark model with hidden local symmetry which also favors the VME dominant for the short range interactions of light quarks. The VME dominance for the short range interactions of light quarks gives a natural explanation of the empiric VME dominance for the interactions between hadrons containing light quarks.

hep-ph↗

arXiv2024

Revealing the mystery of the double charm tetraquark in $pp$ collision

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 two theoretical pictures, i.e. the compact tetraquark and hadronic molecular pictures, we find that the former one exhibits a significantly larger production asymmetry, enabling the unambiguous determination of the tetraquark's internal structure. Additionally, distinctive differences in the transverse momentum and rapidity distributions of $T_{\bar{c}\bar{c}}^-$ and $T_{cc}^+$ cross sections emerge, particularly at $p_\mathrm{T}\approx 2~\mathrm{GeV}$ and $y\approx \pm 6$ at a center-of-mass energy of 14$~\mathrm{TeV}$. The insignificant asymmetry in hadronic molecular picture is because that hadronic molecules are produced in hadronic phase, where the phase space of their constituents needs to be taken into account rigorously. Our work can be extended to the exploration of other double heavy tetraquark candidates, offering a versatile approach to advance our understanding of exotic hadrons.

hep-ph↗

arXiv2024

Investigation of $Λ_c$ States and $(\bar{D}N)$ Molecules Production at EicC and EIC

We explore various $Λ_c$ states, including $Λ_c$, $Λ_c(2595)$, $Λ_c(2940)$, and the predicted $(\bar{D}N)$ hadronic molecular states, in photoproduction and electroproduction to estimate their yields at EicC and EIC. Assuming $Λ_c(2940)$ as either a hadronic molecular state or a three-quark state, our analysis demonstrates that its production rates are of the same order of magnitude, posing challenges in identifying its underlying structure. After considering the integral luminosity, the yields of $Λ_c$ excited states reach $10^6$ to $10^7$ at EicC and EIC. The $(\bar{D}N)$ molecular states with both isospin $I = 0$ and $I = 1$ are also studied, with yields reaching $10^5$, making them likely to be detectable at these facilities.

hep-ph↗

arXiv2024

Production of exotic hadrons in $pp$ and nuclear collisions

Exotic hadrons beyond the conventional quark model have been discovered in the past two decades. Investigations of these states can lead to deep understanding of nonperturbative dynamics of the strong interaction. In this concise review, we focus on the productions of exotic hadrons in $pp$, $p\bar p$, and nuclear collisions. Experimental observations of light nuclei and hypernuclei, as prototypes of hadronic molecules, in heavy ion collisions will also be briefly discussed.

hep-ph↗

arXiv2024

Review of the low-lying excited baryons $Σ^*(1/2^-)$

Strong empirical and phenomenological indications exist for large sea-quark admixtures in the low-lying excited baryons. Investigating the low-lying excited baryon $Σ^*(1/2^-)$ is important to determine the nature of the low-lying excited baryons. We review the experimental and theoretical progress on the studies of the $Σ^*(1/2^-)$. Although several candidates have received intensive discussions, such as $Σ(1620)$ and $Σ(1480)$, their existence needs further confirmation. Following the prediction of the unquenched quark models for the $Σ^*(1/2^-)$, many theoretical works suggested the existence of these states in various processes. Future experimental measurements could shed light on the existence of the low-lying excited $Σ^*(1/2^-)$ state.

hep-ph↗

arXiv2024

Exploration of the LHCb $P_c$ states and possible resonances in a unitary coupled-channel model

We extend our previous study of the interactions of $\bar{D}^{(*)} Λ_c - \bar{D}^{(*)}Σ_c^{(*)}$ within an analytic, unitary, coupled-channel approach by including the $J/ψp$ channel and performing fits to the $J/ψp$ invariant mass distributions in the $Λ_b^0 \to J/ψp K^-$ decay by the LHCb Collaboration. We take into account the contributions of $t$-channel pseudoscalar and vector meson exchanges and $u$-channel baryon exchanges in this work, and a series of bound states and resonances with different spin-parities are dynamically generated. According to the results, four states have a significant impact on the physical observables, with two having a spin-parity of $1/2^-$ and the other two having $3/2^-$. These states can be associated with the LHCb hidden-charm pentaquarks. We further provide the coupling strength between each pole and different channels, which provides some insights on how to search for them in future experiments. Moreover, we also search for poles in higher partial waves up to $J=7/2$ and find indications for the existence of several states with larger widths.

hep-ph↗

arXiv2024

Hints of the $J^{PC}=0^{--}$ and $1^{--}$ $K^*\bar K_1(1270)$ Molecules in the $J/ψ\toϕηη'$ Decay

The primary objective of this study is to investigate hadronic molecules of $K^*\bar K_1(1270)$ using a one-boson-exchange model, which incorporates exchanges of vector and pseudoscalar mesons in the $t$-channel, as well as the pion exchange in the $u$-channel. Additionally, careful consideration is given to the three-body effects resulting from the on-shell pion originating from $K_1(1270)\to K^*π$. Then the BESIII data of the $J/ψ\toϕηη'$ process is fitted using the $K^*\bar K_1(1270)$ scattering amplitude with $J^{PC}=0^{--}$ or $1^{--}$. The analysis reveals that both the $J^{PC}=0^{--}$ and $1^{--}$ assumptions for $K^*\bar K_1(1270)$ scattering provide good descriptions of the data, with similar fit qualities. Notably, the parameters obtained from the best fits indicate the existence of $K^*\bar K_1(1270)$ bound states, denoted by $ϕ(2100)$ and $ϕ_0(2100)$ for the $1^{--}$ and $0^{--}$ states, respectively. The current experimental data, including the $η$ polar angular distribution, cannot distinguish which $K^*\bar K_1(1270)$ bound state contributes to the $J/ψ\toϕηη'$ process, or if both are involved. Therefore, we propose further explorations of this process, as well as other processes, in upcoming experiments with many more $J/ψ$ events to disentangle the different possibilities.

hep-ph↗

arXiv2024

Possible $Σ_c^* \barΣ$ molecular states

We investigate the possibility of deuteron-like $Σ_c^*\barΣ$ bound states within the one-boson-exchange model and systematically analyze the effects of the contact-range $δ^{3}(\vec{r}\,)$ potential, the tensor term from the vector-meson exchange, and nonlocal potentials due to the dependence on the sum of the initial and final state center-of-mass momenta. We find that the pion-exchange potential including the $δ^{3}(\vec{r}\,)$ term and the tensor term of the $ρ$-exchange potential exhibit comparable magnitudes but opposite signs for any $S$-wave baryon-antibaryon systems. For the $Σ_c^*\barΣ$ system, it is most likely to form bound states with mass around 3.7 GeV in the $I(J^P)=0(2^-)$ and $1(2^-)$ channels.

hep-ph↗

arXiv2023

Dynamical origin of universal two-pole structures and their light quark mass evolution

Two-pole structures refer to the fact that two dynamically generated states are located close to each other between two coupled channels and have a mass difference smaller than the sum of their widths. Thus, the two poles overlap in the invariant mass distribution of their decay products, creating the impression that only one state exists. This phenomenon was first noticed for the $Λ(1405)$ and the $K_1(1270)$, and then for several other states. This report explicitly shows how the two-pole structures emerge from the underlying universal chiral dynamics describing the coupled-channel interactions between a heavy matter particle and a pseudo-Nambu-Goldstone boson. Furthermore, we predict similar two-pole structures in other systems dictated by chiral symmetry, such as the isospin $1/2$ $\bar{K}Σ_c-πΞ'_c$ coupled channel, awaiting experimental discoveries.

hep-ph↗

arXiv2023

Two-pole structures as a universal phenomenon dictated by coupled-channel chiral dynamics

In the past two decades, one of the most puzzling phenomena discovered in hadron physics is that a nominal hadronic state can actually correspond to two poles on the complex energy plane. This phenomenon was first noticed for the $Λ(1405)$, then for $K_1(1270)$, and to a lesser extent for $D_0^*(2300)$. In this Letter, we show explicitly how the two-pole structures emerge from the underlying universal chiral dynamics describing the coupled-channel interactions between heavy matter particles and pseudo Nambu-Goldstone bosons. In particular, the fact that two poles appear in between the two dominant coupled channels can be attributed to the particular form of the leading order chiral potentials of the Weinberg-Tomozawa form. Their lineshapes overlap with each other because the degeneracy of the two coupled channels is only broken by explicit chiral symmetry breaking of higher order. We predict that for light-quark~(pion) masses heavier than their physical values (e.g., about 200 MeV in the $Λ(1405)$ case studied), the lower pole becomes a virtual state, which can be easily verified by future lattice QCD simulations. Furthermore, we anticipate similar two-pole structures in other systems, such as the isopin $1/2$ $\bar{K}Σ_c-πΞ'_c$ coupled channel, which await for experimental discoveries.

hep-ph↗

arXiv2023

Effects of $N(2080){3/2}^-$ and $N(2270)3/2^-$ molecules on $K^\ast Σ$ photoproduction

In the present work, we re-analyze the available data for $γp\to K^{\ast +}Σ^0$ and $γp \to K^{\ast 0}Σ^+$ by considering the contributions from the $N(2080){3/2}^-$ and $N(2270)3/2^-$ molecules instead of any nucleon resonances in the $s$ channel, where the $N(2080)3/2^-$ was proposed to be a $K^\ast Σ$ molecule as the strange partner of the $P_c^+(4457)$ hadronic molecular state, and the $N(2270)3/2^-$ was assumed to be a $K^*Σ^*$ molecule as the strange partner of the $\bar{D}^\ast Σ^\ast_c$ bound states that are predicated as members in the same heavy-quark spin symmetry multiplet as the $P_c$ states. It turns out that all the available cross-section data can be well reproduced, indicating that the molecular structures of the possible $N(2080){3/2}^-$ and $N(2270)3/2^-$ states are compatible with the available data for $K^\astΣ$ photoproduction reactions. Further analysis shows that for both $γp\to K^{\ast +}Σ^0$ and $γp \to K^{\ast 0}Σ^+$ reactions, the $N(2080){3/2}^-$ exchange provides dominant contributions to the cross-sections in the near-threshold energy region, and significant contributions from the $N(2270)3/2^-$ exchange to the cross-sections in the higher energy region are also found. Predictions of the beam asymmetry $Σ$, target asymmetry $T$, and recoil baryon asymmetry $P$ are presented and compared with those from our previous work. Measurements of the data on these observables are called on to further constrain the reaction mechanisms of $K^\astΣ$ photoproduction reactions and to verify the molecular scenario of the $N(2080){3/2}^-$ and $N(2270)3/2^-$ states.

nucl-th↗

arXiv2023

Covariant orbital-spin scheme for any spin based on irreducible tensor

In hadron spectrum physics, the partial wave analysis is a primary method used to extract properties of hadronic resonances. The covariant orbital-spin coupling scheme holds unique advantages over other partial wave methods due to its Lorentz covariant form and determined orbital-spin quantum numbers. This paper presents a general form of the covariant orbital-spin coupling scheme based on the irreducible tensor of the homogeneous proper Lorentz group and its little groups. A systematic procedure for constructing partial wave amplitude in a Lorentz covariant way is provided, which can be applied to both massive and massless particles. Specific examples are also included.

hep-ph↗

arXiv2023

Molecular states in $D_s^{()+}Ξ_c^{(',)}$ systems

The possible hadronic molecules in $D_s^{(*)+}Ξ_c^{(',*)}$ systems with $J^P=1/2^-,3/2^-$ and $5/2^-$ are investigated with interactions described by light meson exchanges. By varying the cutoff in a phenomenologically reasonable range of $1\sim2.5$ GeV, we find ten near-threshold (bound or virtual) states in the single-channel case. After introducing the coupled-channel dynamics of $D_s^{+}Ξ_c$-$D_s^{+}Ξ_c^{'}$-$D_s^{*+}Ξ_c$-$D_s^{+}Ξ_c^{*}$-$D_s^{*+}Ξ_c^{'}$-$D_s^{*+}Ξ_c^{*}$ systems, these states, except those below the lowest channels in each $J^{P}$ sector, move into the complex energy plane and become resonances in the mass range of $4.43\sim4.76$ GeV. Their spin-parities and nearby thresholds are $1/2^-(D_s^{+}Ξ_c)$, $1/2^-(D_s^{+}Ξ_c^{'})$, $1/2^-(D_s^{*+}Ξ_c)$,$1/2^-(D_s^{*+}Ξ_c^{'})$, $1/2^-(D_s^{*+}Ξ_c^{*})$ , $3/2^-(D_s^{*+}Ξ_c)$, $3/2^-(D_s^{+}Ξ_c)$, $3/2^-(D_s^{*+}Ξ_c^{'})$, $3/2^-(D_s^{*+}Ξ_c^{*})$, and $5/2^-(D_s^{*+}Ξ_c^{*})$. The impacts of the $δ(r)$-term in the one-boson-exchange model on these states are presented. Setting $Λ=1.5$ GeV as an illustrative value, it is found that $1/2^-(D_s^{+}Ξ_c)$ is a stable bound state (becoming unstable if turning on the coupling to lower channels), $1/2^-(D_s^{*+}Ξ_c)$ and $3/2^-(D_s^{*+}Ξ_c)$ are physical resonances in both cases of including or excluding the $δ(r)$-term, while the other seven states are physical resonances or ``virtual-state-like" poles near thresholds, depending on including the $δ(r)$-term or not. In addition, the partial decay widths of the physical resonances are provided. These double-charm hidden-strangeness pentaquark states, as the partners of experimentally observed $P_c$ and $P_{cs}$ states, can be searched for in the $D^{(*)}Λ_c$ final states in future.

hep-ph↗