arXiv subjects

Xiaoyun Chen

Publications and source records attributed to Xiaoyun Chen.

At least 19 recordsLinked to original sources

arXiv2025

Investigation of Resonances in the $Σ({1/2}^{-})$ System Based on the Chiral Quark Model

In this work, we investigate the resonance structures in the $Σ(1/2^-)$ system from both three-quark and five-quark perspectives within the framework of the chiral quark model. An accurate few-body computational approach, the Gaussian Expansion Method, is employed to construct the orbital wave functions of multiquark states. To reduce the model dependence on parameters, we fit two sets of parameters to check the stability of the results. The calculations show that our results remain stable despite changes in the parameters. In the three-quark calculations, two $Σ(1/2^-)$ states are obtained with energies around 1.8~GeV, which are good candidates for the experimentally observed $Σ(1750)$ and $Σ(1900)$. In the five-quark configuration, several stable resonance states are identified, including $Σπ$, $N \bar{K}$, and $N \bar{K}^{*}$. These resonance states survive the channel-coupling calculations under the complex-scaling framework and manifest as stable structures. Our results support the existence of a two-pole structure for the $Σ(1/2^-)$ system, predominantly composed of $Σπ$ and $N \bar{K}$ configurations, analogous to the well-known $Λ(1380)$-$Λ(1405)$ ($Σπ$-$N \bar{K}$) system. On the other hand, although the energy of the $N \bar{K}^{*}$ configuration is close to that of $Σ(1750)$ and $Σ(1900)$, the obtained width is not consistent with the experimental values. This suggests that the $N \bar{K}^{*}$ state needs to mix with three-quark components to better explain the experimental $Σ(1750)$ and $Σ(1900)$ states. According to our decay width calculations, the predicted two resonance states are primarily composed of $Σπ$ and $N \bar{K}$, with their main decay channel being $Λπ$.

hep-ph↗

arXiv2025

$Υ(5S)$ in the unquenched quark model

The observation of the $Υ(10753)$ state by Belle II Collaboration has sparked significant interest in the theoretical understanding of such states within the context of hadron physics. Considering the similar mass and the decay with, as well as the same quantum numbers $J^{PC}=1^{--}$ with the $Υ(10860)$ state, which is referred to be the $Υ(5S)$ in PDG, in this work, we try to calculate the mass of the $Υ(5S)$ state. The model used to predict the high-energy spectrum of these states generally involves a constituent quark model, which can describe a variety of properties of hadrons containing heavy quarks. In the framework of the unquenched quark model, a coupled-channel calculation is employed to explore the effect of open-bottom meson-meson thresholds on the $Υ(10860)$ state. The hypothesis is that coupled-channel effects could be large enough to create new dynamically generated states, thus potentially explaining the nature of the $Υ(10860)$ state, as well as whether the $Υ(10860)$ and $Υ(10753)$ is the same state. The results indicate that unquenched effects play a crucial role in explaining the $Υ(10860)$ state, providing a plausible mechanism for its formation. Besides in our calculations, the $Υ(10860)$ and $Υ(10753)$ may be two different states.

hep-ph↗

arXiv2025

A study on the properties of hidden-charm pentaquarks with double strangeness

Motivated by the LHCb observations of $P_c$ and $P_{cs}$ states, we systematically investigate the hidden-charm double-strange pentaquark system ($nssc\bar{c}$) using the resonating group method within the quark delocalization color screening model (QDCSM). By dynamically incorporating channel coupling effects, five resonance states are identified with $J^P = 1/2^-$ and $3/2^-$. Their masses, widths, and dominant decay channels are predicted, providing critical guidance for future experimental searches.

hep-ph↗

arXiv2025

Exploring the nature of $η_{1}(1855)$ and it's partner in a chiral quark model

Inspired by the recent experimental discoveries of $X(3872)$ ($c\bar{q}$-$q\bar{c}$) and $T_{cc}$ ($c\bar{q}$-$c\bar{q}$), we systematically study two four-quark systems: the $K K_1$ ($q\bar{s}$-$q\bar{s}$) system and the $K \bar{K}_1$ ($q\bar{s}$-$s\bar{q}$) system, which is a candidate for the recently observed $η_1(1855)$. Within the framework of an accurate few-body calculation method (GEM), we employ the chiral quark model to simultaneously consider the molecular and diquark structures of these two multiquark systems and include their channel coupling effects. Our results show that the $K \bar{K}_1$ system remains a scattering state. On the other hand, due to the presence of a good-diquark structure in the $K K_1$ system, we obtain a bound state in the coupled-channel calculation. The primary contribution to the binding energy comes from the exchange of $π$-meson and $σ$-meson. The inter-quark distance indicates that it is a compact four-quark structure.

hep-ph↗

arXiv2025

Investigating the nature of $N(1535)$ and $Λ(1405)$ in a quenched chiral quark model

In this work, we systematically study $N(1440)$, $N(1535)$, and $Λ(1405)$ in both the quenched three-quark and five-quark frameworks using the Gaussian Expansion Method (GEM) within the chiral quark model. Our calculations show that $N(1535)$ can be reproduced as a three-quark state ($N(1P)$), while $N(1440)$ and $Λ(1405)$ cannot be accommodated as the three-quark candidates, ($N(2S)$ and $Λ(1P)$), respectively. In the five-quark framework, we find that the $ΛK$ state for $N(1535)$ can not form a bound state, while in the $N\bar{K}$ channel there will $Λ(1405)$ form a shallow bound state. Based on the complex-scaling method, we performed complete coupled-channels calculations and obtained six resonance states with energies ranging from 1.8 GeV to 2.2 GeV, in addition with one bound state located around $Σπ$ channel. However, neither molecular candidates in $ΛK$ channel for $N(1535)$ nor $N\bar{K}$ for $Λ(1405)$ are included in these states. This is because the strong coupling between $N\bar{K}$ and $Σπ$ will make the $N\bar{K}$ unbound, while the weak coupling between $ΛK$ and $ΣK$ can not help form a stable structure around $ΛK$ threshold. Thus, under the quenched quark model, our results support $N(1535)$ as a three-quark state, while $N(1440)$ is neither a three-quark nor a five-quark state. In addition, we find that although $Λ(1405)$ can be primarily a five-quark state, it requires a mixture of three-quark and five-quark components for stability. In the future, an exploration on the mixing effects between bare baryons with these relevant two-body hadronic channel components will be carried out to further test our conclusions.

hep-ph↗

arXiv2025

Study of the $c\bar{c}s\bar{s}$ system in the chiral quark model

Recently, a charmonium $X(3960)$ in $B$ decays in the $D_s^+D_s^-$ invariant-mass spectrum is discovered by the LHCb Collaboration with the quantum number $J^{PC}=0^{++}$. Motivated by the discovery, in this work, we systematically investigated the $c\bar{c}s\bar{s}$ tetraquark states with the quantum numbers $J^{PC}=0^{++}, 1^{++}, 1^{+-}, 2^{++}$ in the framework of the chiral quark model(CQM). In our calculations, we considered the meson-meson structure of the tetraquark states and the diquark-antidiquark structure, as well as the channel-coupling of all channels of these two configurations are considered in this work. For example, all color structures including color singlet, hidden color channel, and the mixing of them are also taken into account. The numerical results indicates that no bound states were found in our model. But there exist several resonant states by using the stabilization method, the real scaling method (RSM) so called. Among these states, the $0^{++}$ resonant state with mass 3927 MeV matches very well with the energy of the newly discovered exotic state $X(3960)$ reported by the LHCb collaboration. As a result, our calculations suggest that $X(3960)$ can be interpreted as a $c\bar{c}s\bar{s}$ tetraquark state with quantum number $J^{PC}=0^{++}$. Apart form that, we also find several resonance states with mass 4179 MeV, 4376 MeV with $0^{++}$. For $1^{++}$, there is likely one resonance state in the energy range of 4310$\sim$4336 MeV, along with two resonance states at the energy of 4395 MeV and 4687 MeV, respectively. Besides, two resonance states at 4300 MeV and 4355 MeV for $1^{+-}$, as well as one state at 4788 MeV for $2^{++}$, are found, which are likely to be new exotic states. More experimental data is needed to confirm the existence of these resonance states.

hep-ph↗

arXiv2024

Probing the nature of the anticharmed-strange pentaquark states: mass spectra, decays, and magnetic moments

Within the framework of the quark delocalization color screening model, a systematic investigation of the anticharmed-strange pentaquark system is performed using the resonance group method. The currently estimations predict three bound states with estimated masses to be 2886 MeV, 3039 MeV, and 3153 MeV, respectively. Additionally, three resonance states are identified in various scattering phase shifts processes. Among them, two resonance states $ΣD$ and $Σ^{\ast}D^{\ast}$ with quantum number $\frac{1}{2}(\frac{1}{2}^{-})$ are detected in channels $ND_{s}^{\ast}$ and $ND$, and $ΣD^{\ast}$ and $ΛD$, with masses and decay widths of ($M_{R}=3053\sim3055$ MeV, $T_{total}=13.0\sim13.4$ MeV) and ($M_{R}=3389\sim3390$ MeV, $T_{total}=10.4$ MeV), respectively. In the $ΛD^{\ast}$ and $ΣD^{\ast}$ channels, a resonance state with quantum number $\frac{1}{2}(\frac{3}{2}^{-})$ is discovered, with its mass and decay width being $3250\sim3252$ MeV and 4.4 MeV, respectively. These predicted pentaquark states have $\bar{c}snnn$ quark compositions, allowing them to be recognized as genuine pentaquark states. To validate these predictions, it is expected that upcoming experiments will further explore the predicted resonance and bound states in these possible decay channels.

hep-ph↗

arXiv2024

The light quarkonium and charmonium mass shifts in an unquenched quark model

The unquenched quark model for the light quarkonium and the charmonium states is explored in the present work. The quark-pair creation operator in the $^3P_0$ model, which mix the two-quark and four-quark components is modified by considering the effects of the created quark pair's energy, as well as the separation between the created quark pair and the valence quark pair. All the wave functions needed including the mesons and the relative motion between two mesons are all obtained by solving the corresponding Schrödinger equation with the help of the Gaussian expansion method. Our aim of the present work is to find a new set of parameters which can give a good description of the mass spectrum of the low-lying light quarkonium and charmonium states. Moreover, some exotic states, for example $X(3872)$ can be described well in the unquenched quark model.

hep-ph↗

arXiv2024

Dynamical study of $D^{}DK$ and $D^{}D \bar{D}$ systems at quark level

Inspired by that Belle\uppercase\expandafter{\romannumeral2} Collaboration recently reported $T_{cc}$, which can be interpreted as a molecular $DD^{*}$, we investigated the trihadron system of $T_{cc}$ partner with $IJ^{P}$=$01^{-}$ in the framework of a chiral quark model. It's widely accepted that the main component of $X(3872)$ contains the molecular $\bar{D}D^{*}$, while the main component of $D_{s0}^{*}(2317)$ is molecular $DK$. Based on these three well-known exotic states, $T_{cc} (DD^{*})$, $X(3872) (\bar{D}D^{*})$ and $D_{s0}^{*}(2317) (DK)$, we dynamically investigate $D^{*}DK$ and $DD^{*}\bar{D}$ systems at quark level to search for possible bound states. The results show that both of them are bound states, in which the binding energy of the molecular state $DD^*K$ is relatively small, only 0.8 MeV, while the binding energy of $DD^*\bar{D}$ is up to 1.9 MeV. According to the calculation results of the Root-square-mean distances, the spatial structure of the two systems shows obvious ($DD^*$)-($\bar{D}$/$K$) structure, in which $D$ is close to $D^*$ while $DD^*$ as a whole is relatively distant from the third hadron ($\bar{D}$/$K$), which are similar to the nucleon-electron structure. As a result, we strongly recommend that these bound states $DD^*\bar{D}$ and $DD^*K$ are searched for experimentally.

hep-ph↗

arXiv2024

Equivalence among color singlet, color octet and diquark structure in a chiral quark model

Since the quark model was put forward, theoretical researchers have always attached great importance to the study of hidden color channels (including color octets and diquark structure). Because of the influence of color Van der waals forces, the hidden color channel itself has strong attraction, which provides a dynamic mechanism for the formation of resonance state or bound state. In this paper, taking the $T_{cc}$ system as an example, under the framework of multi-Gaussian expansion method, a set of relatively complete color singlets (that is, the ground state of the color singlet plus its corresponding higher-order component) is used to replace the contribution of the color octet. Similarly, we endeavor to replace the diquark structure with a relatively complete set of molecular states, encompassing both the ground state and excited states. Our results demonstrate that the color octet structure can be effectively replaced by a set of relatively complete color singlet bases, while the diquark structure cannot be entirely substituted by an equivalently comprehensive set of molecular state bases.

hep-ph↗

arXiv2023

Investigation of the analog of the $P_{c}$ states-the doubly charmed molecular pentaquarks

Motivated by the LHCb Collaboration's observation of a doubly charmed tetraquark state $T_{cc}(3875)$, we systematically investigate the existence of doubly charmed pentaquark states using the resonating group method based on the QDCSM framework. The effective potential of the two involved hadrons and the bound state dynamics are included in the present work. Moreover, we have also calculated the scattering phase shifts of open channels by channel coupling to look for possible resonance states. Our estimations indicate that there is a bound state in $I(J^{P})=\frac{3}{2}(\frac{5}{2}^{-})$, with a mass of $4461.7$ MeV. Additionally, five resonance states can be obtained by coupling the open channel, which are $Ξ_{cc}ρ$ and $Σ_{c}D^{\ast}$ with $I(J^{P})=\frac{1}{2}(\frac{1}{2}^{-})$, $Λ_{c}D^{\ast}$ and $Σ_{c}D^{\ast}$ with $I(J^{P})=\frac{1}{2}(\frac{3}{2}^{-})$ and $Σ_{c}D^{\ast}$ with $I(J^{P})=\frac{3}{2}(\frac{1}{2}^{-})$respectively. The existence of these predicted doubly charmed pentaquark states needs to be supported by experimental measurements and discoveries. We hope that some experiments can find evidence of these states.

hep-ph↗

arXiv2023

Maximizing Metapopulation Growth Rate and Biomass in Stream Networks

We consider the logistic metapopulation model over a stream network and use the metapopulation growth rate and the total biomass (of the positive equilibrium) as metrics for different aspects of population persistence. Our objective is to find distributions of resources that maximize these persistence measures. We begin our study by considering stream networks consisting of three nodes and prove that the strategy to maximize the total biomass is to concentrate all the resources in the most upstream locations. In contrast, when the diffusion rates are sufficiently small, the metapopulation growth rate is maximized when all resources are concentrated in one of the most downstream locations. These two main results are generalized to stream networks with any number of patches.

math.DS↗

arXiv2023

Charmonium mass shifts in an unquenched quark model

In this paper, we performed a coupled-channel calculation and evaluated the mass shifts for all $1S$, $2S$, $1P$, $2P$ and $1D$ charmonium valence states below 4 GeV, by incorporating the four-quark components ($D$, $D^*$, $D_s$ and $D_s^*$ meson pairs) into the quark model. The valence-continuum coupling is provided by the $^3P_0$ quark-pair creation model. The induced mass shifts appear to be large and negative with the original transition operator in $^3P_0$ model, which raised up challenges for the valence quark model. More QCD-motivated models should be employed for the quark-pair creation Hamiltonian. So herein, we recalculated the mass shifts with the improved $^3P_0$ transition operator introduced in our previous work and the mass shifts are reduced by $75\%$ averagely. Besides, as a exercise, we adjust the confinement parameter $Δ$ and recalculate the spectrum of the charmonium states. The masses of some charmonium states are reproduced well.

hep-ph↗

arXiv2023

Non-stationary Lattice Anderson Model with Non-local Laplacian and Correlated White Noise

We study the non-stationary Anderson parabolic problem on the lattice $Z^d$, i.e., the equation \begin{equation}\label{andersonmodel} \begin{aligned} \frac{\partial u}{\partial t} &=\varkappa \mathcal{A}u(t,x)+ξ_{t}(x)u(t,x) u(0,x) &\equiv 1, \, (t,x) \in [0,\infty)\times Z^d. \end{aligned} \end{equation} Here $\mathcal{A}$ is non-local Laplacian, $ξ_t (x), \ t \geq 0, \ x \in Z^d$ is the family of the correlated white noises and $\varkappa >0$ is the diffusion coefficient. The changes of $\varkappa$ (large versus small) are responsible for the qualitative phase transition in the model. At the first step the analysis of the model is reduced to the solution of the stochastic differential equation(SDE) (in the standard Itô's form) on the weighted Hilbert space $l^2(Z^d,μ)$ with appropriate measure $μ$. The equations of first two moments of the solution $u(t,x)$ are derived and studied using the spectral analysis of the corresponding Schrödinger operators with special class of the positive definite potentials. The analysis reveals several bifurcations depending on the properties of the kernel of $\mathcal{A}$ and the correlation function in the potential.

math.PR↗

arXiv2022

Possible charmed-strange molecular pentaquarks in quark delocalization color screening model

Inspired by the states $T_{c\bar{s}0}^{a}(2900)^{0}$ and $T_{c\bar{s}0}^{a}(2900)^{++}$ reported by the LHCb Collaboration, we carry out a systematical investigation of the charm-strange pentaquark system using resonance group method in the quark delocalization color screening model. The present results predict the existence of some bound states and resonance states with support from the study of the mass spectrum and the decay properties. Both $Σ_{c}^{\ast}K^{\ast}$ with $I(J^{P})=\frac{1}{2}(\frac{5}{2}^{-})$ and $ΔD_{s}^{\ast}$ with $I(J^{P})=\frac{3}{2}(\frac{5}{2}^{-})$ are bounded by channel coupling calculation. Moreover, the resonance state $Σ_{c}K^{\ast}$ with $I(J^{P})=\frac{1}{2}(\frac{1}{2}^{-})$ and $I(J^{P})=\frac{1}{2}(\frac{3}{2}^{-})$ are available in QDCSM, the masses and the total decay widths of which are ($R^{\prime}=3342\sim3346$ MeV, $Γ_{Total}=25.5$ MeV) and ($R^{\prime}=3333$ MeV, $Γ_{Total}=3.3$ MeV), respectively. In addition, the resonance state $ΔD_{s}^{\ast}$ with $I(J^{P})=\frac{3}{2}(\frac{1}{2}^{-})$ is also obtained, the mass and the decay width of this state are 3343 MeV and 0.01 MeV, respectively. These predicted new exotic states may provide new ideas for experimental searches and we sincerely expect more experimental and theoretical research to verify and understand the charm-strange pentaquark states in the future.

hep-ph↗

arXiv2022

The newly observed $Υ(10753)$ as a tetraquark state in a chiral quark model with scalar nonet exchange

Recently, Belle\uppercase\expandafter{\romannumeral2} Collaboration firstly reported a new resonance $ωχ_{bJ}$ in the processes of $e^{+}e^{-} \rightarrow ωχ_{bJ}$ at center-of-mass energies $\sqrt{s}=10.745$ GeV. Given the Born cross section similar with the previously reported $Υ(10753)$, the new resonance $ωχ_{bJ}$ may have be $Υ(10753)$. From the perspectives of traditional $Υ(nS)$ meson and exotic tetraquark $b\bar{q}q\bar{b}$ state with the $J^{PC}$ = $1^{--}$, we tentatively investigate the $Υ(10753)$ by solving Schrödinger equation in the framework of the chiral quark model. Numerical results for the meson show that the mass of $Υ(5S)$ is up to 10.86 GeV and unsuitable for the candidate of $Υ(10753)$. On the other hand, not only the two kinds of molecular structure ($b\bar{b}$-$q\bar{q}$, $b\bar{q}$-$q\bar{b}$) but also the \da~structure ($\bar{b}\bar{q}$-$qb$) are considered into our tetraquark calculation with the help of Gaussian expansion method. When a fully-channel coupling is performed using the real-scaling method (stabilization method), we get a stable resonance $^1R_{1}(10770)$ ( $^{2S+1}R_J$ ) with a great component of the diquark-antidiquark state. Combined with the mass and width of $^1R_{1}(10770)$, it may be a good candidate for experimental $Υ(10753)$. Besides, several resonance states ranging from 10.82 GeV to 10.96 GeV are obtained, which are expected to be further verified in future experiments.

hep-ph↗

arXiv2022

Double-heavy tetraquarks with strangeness in the chiral quark model

Recently, some progresses have been made on the double-heavy tetraquarks in the experiments, such as $T_{cc}$ reported by LHCb Collaboration, and $X_{cc\bar{s}\bar{s}}$ reported by the Belle Collaboration. Coming on the heels of our previous work about $T_{cc}$ and $T_{bb}$, we present a study on the bound states and the resonant states of its companions $QQ\bar{q}\bar{s}$ ($Q=c,b; q=u, s$) tetraquarks with strange flavor in the chiral quark model. Two pictures, one with meson-meson picture, another with diquark-antidiquark picture and their couplings are considered in our calculations. Isospin violation is neglected herein. Our numerical analysis indicates that only the state $bb\bar{u}\bar{s}$ with $\frac{1}{2}(1^+)$ is bound, with the binding energy 3.5 MeV. Besides, we also find some resonant states for the double-heavy strange tetraquarks with the real scaling method.

hep-ph↗

arXiv2022

Investigation of the bottom analog of the Zcs(3985) state

Motivated by the recent discovery of the hidden charm exotic state with strangeness by the BESIII and LHCb Collaborations, we study the $S$ wave strange hidden bottom tetraquark in two kinds of quark models. Both meson-meson and diquark-antidiquark configurations are taken into account. The numerical results indicate that there is no bound state in both quark models. However, several resonance states have been predicted. Three resonance states with $I(J^{P})=\frac{1}{2}(0^{+})$ are found, the energy ranges of which are $10479\sim 10550$, $10528\sim 10632$, and $10597\sim 10681$ MeV, respectively. Three resonance states with $I(J^{P})=\frac{1}{2}(1^{+})$ are predicted to be located in $10491\sim 10675$, $10502\sim 10679$, and $10522\sim 10723$ MeV, respectively. Moreover, there also exist a resonance with $I(J^{P})=\frac{1}{2}(2^{+})$ and the mass is estimated to be $10531\sim 10680$ MeV. All these predicted states in the present work should be accessible for the further experiments in LHCb

hep-ph↗