arXiv subjects

Xian-Hui Zhong

Publications and source records attributed to Xian-Hui Zhong.

At least 19 recordsLinked to original sources

arXiv2026

Hidden charm pentaquarks and the nature of $P_{c}$ states observed at LHCb

We carry out a unified study of the low-lying $1S$-wave compact states and hadronic molecules composed of hidden charm pentaquarks $qqqc\bar{c}$ ($q=u,d$) within a semirelativistic potential quark model. Apart from the linear confinement and one-gluon exchange potential between quarks and/or antiquarks, one-boson exchange potential is also included for baryon and meson clusters within the pentaquark system. We also evaluate the fall-apart decays by combining the obtained spectra within the quark exchange model. It is found that the $P_c (4312)^+$, $P_c (4440)^+$, and $P_c (4457)^+$ observed by the LHCb Collaboration in 2019 can be well explained by the hadronic molecules of $[Σ_c\bar{D}]_{1/2^-}^{1/2}(4318)$, $[Σ_c\bar{D}^*]_{1/2^-}^{1/2}(4437)$, and $[Σ_c\bar{D}^*]_{3/2^-}^{1/2}(4458)$, respectively. Meanwhile, $P_c(4380)^+$ reported by LHCb in 2015 may be assigned as the molecule $[Σ_c^*\bar{D}]_{3/2^-}^{1/2}(4382)$, except that it turns to be a narrow state other than a broad one shown by the experimental data. Our study shows that the $σ$- and $ρ$-meson exchanges are crucial for the formation of $Σ_c^{(*)}\bar{D}^{(*)}$ bound states with isospin $I=1/2$. Depending on the potential strength of the $σ$ exchange, there may exist very shallow bound states of $Λ_c\bar{D}^{(*)}$ with isospin $I=1/2$ and $Σ_c^{(*)}\bar{D}^{(*)}$ with isospin $I=3/2$. Our study may provide useful information for further exploring the hidden-charm pentaquarks in future experiments.

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arXiv2026

$Ω_c$ baryon spectrum and strong decays in a constituent quark model

In this work, we study the $Ω_c$ baryon spectrum up to the $2P$ excitations within a semi-relativistic constituent quark potential model, where the mixing between different configurations with the same spin-parity numbers is dynamically considered. Furthermore, the strong decay properties for the excited $Ω_c$ states are evaluated within an improved chiral quark model by including the relativistic correction term. In a unified framework, we provide a reasonable explanation of the widths, masses, and mass splittings, for the newly observed $Ω_c$ resonances $Ω_c(3000)$, $Ω_c(3050)$, $Ω_c(3065)$, $Ω_c(3090)$, $Ω_c(3120)$, $Ω_c(3185)$, and $Ω_c(3327)$. It is found that the configuration mixing is crucial for understanding the strong decay properties and mass splittings, while the relativistic correction term of the strong transition operator plays an important role in the states dominated by the radial excitations. We expect our study can provide useful references for establishing a more abundant $Ω_c$ spectrum.

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arXiv2026

Singly heavy tetraquarks

In this work, we carry out a systematic study of the spectra of the $1S$-wave states for the whole singly-heavy tetraquark systems within a semi-relativistic hybrid quark potential model, in which both the one-gluon exchange (OGE) and one-boson exchange (OBE) interactions are included. Furthermore, the fall-apart decays are evaluated with the quark exchange model by combining the obtained spectra. It is found that besides the OGE potentials, the OBE potentials play crucial roles for describing the spectrum. All of our obtained states lie far above the lowest dissociation meson-meson threshold. They are compact states with relatively narrow fall-apart widths $\sim 1-120$~MeV. The $D_{s0}(2317)$, $D_{s1}(2460)$, $T_{b\bar{s}}(5568)$, and $T_{c\bar{s}}(2327)$ resonances reported from experiments cannot be explained as compact tetraquarks. While the $T_{\bar{c}\bar{s}0}(2870)$ and $T_{c\bar{s}0}(2900)$ favor the tetraquark states with $IJ^P=00^+$ and $10^+$, i.e. $T_{(\bar{c}\bar{s}[ud])0^+}^0(2919)$ and $T_{(cn\{\bar{s}\bar{n}\})0^+}^{1}(2922)$, respectively. More singly-heavy tetraquark states have good potentials to be observed in some of their dominant decay channels in experiments.

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arXiv2026

Higher excited charmed and charmed-strange mesons in an unquenched quark model

In this paper, as a continuation of our previous work, we systematically study the mass spectra and OZI-allowed strong decays of the higher $3S$-, $2P$-, $2D$-, and $1F$-wave charmed and charmed-strange mesons within a unified unquenched quark model. It is found that for most of the higher excitations, the masses are significantly shifted down by the coupled-channel effects. The newly observed $D_{s1}(2933)^+$ reported by the LHCb collaboration could be identified as the low-mass axial-vector state $D_s(2P_1)$ via the $2^1P_1-2^3P_1$ mixing. For the broad structure $D_{sJ}(3040)^+$ observed earlier by the \emph{BABAR} collaboration, the $D_s(3^1S_0)$ assignment seems to be favored over the high-mass mixed state $D_s(2P_1^\prime)$. Meanwhile, the $D(3000)^0$ signals observed at LHCb cannot be well understood with any $3S$, $2P$, $2D$, or $1F$ assignments in the $D$-meson family. Our predicted masses and decay properties of the missing higher $D$ and $D_s$ mesons may provide useful information for future experimental searches.

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arXiv2026

Understanding the 1P- and 2S-wave nucleon resonances within the extended Lee-Friedrichs Model

We present a unified desciption of the low-lying $1P$- and $2S$-wave nucleon resonance within the framework of an extended Lee-Friedrichs scheme. By incorporating the coupled-channel dynamics between bare quark-model states and the $πN$, $πΔ$ and $ηN$ meson-baryon continua, we examine the mass shifts and structural properties of these excited states. We demonstrate that when the model parameters are calibrated to match the $1P$-wave spectrum and their widths, the pole associated with the bare $2S$ state is naturally shifted downward to the mass region of physical Roper resonance--$N(1440)$, thereby offering a dynamical explanation for the long-standing level-inversion problem. An approximate analysis of compositeness and elementariness reveals that the Roper resonance contains a significant meson-baryon continuum states, consistent with the picture of a bare core heavily dressed by meson-baryon cloud. Simultaneously, the pole positions and properties of five $1P$-wave resonances--$N(1535)$, $N(1650)$, $N(1520)$, $N(1700)$ and $N(1675)$ are successfully reproduced. Our results highlight the essential role of coupled-channel effects in shaping the nucleon spectrum and provide a consistent microscopic insight into the interplay between internal quark degrees of freedom and external hadronic fields.

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arXiv2026

All-heavy tetraquarks with different flavors

In a nonrelativistic potential quark model framework, we carry out a precise calculation of the mass spectrum of the all-heavy tetraquarks with different flavors, $bb\bar{b}\bar{c}$, $cc\bar{c}\bar{b}$, $bb\bar{c}\bar{c}$, and $bc\bar{b}\bar{c}$, by adopting the explicitly correlated Gaussian method. A complete mass spectrum for the $1S$ states is obtained. For the $bb\bar{b}\bar{c}$, $cc\bar{c}\bar{b}$, $bb\bar{c}\bar{c}$, and $bc\bar{b}\bar{c}$ systems, the $1S$ states are predicted to lie in the mass ranges of $ \sim(16.06,16.14)$, $\sim(9.65,9.74)$, $\sim(12.89,12.94)$, and $\sim(12.75,12.99)$~GeV, respectively.Moreover, by using the obtained masses and wave functions, we evaluate the fall-apart decay properties within a quark-exchange model.The results show that the $1S$ states of the all-heavy tetraquarks with different flavors may have narrow fall-apart decay widths,which ranging from a few tenths to several MeV. Some all-heavy tetraquarks with different flavors may have good potentials to be established at LHC in their optimal fall-apart decay channels, such as $ΥJ/ψ$, $ΥB_c^-$, and $J/ψB_c^+$.

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arXiv2026

Fully-strange tetraquarks: fall-apart decays and experimental candidates

We presents a systematic analysis of the fall-apart decays for the $1S$, $1P$, and $2S$-wave fully-strange tetraquark states. It shows that most of the fully-strange tetraquark states have a relatively narrow fall-apart decay width of $\mathcal{O}(10)$ MeV. The newly observed axial-vector state $X(2300)$ at BESIII may favor the low-lying $1S$-wave $1^{+-}$ state $T_{(4s)1^{+-}}(2323)$, while the $X(2500)$ resonance observed in the earlier BESIII experiment may favor the low-lying $1P$-wave $0^{-+}$ state $T_{(4s)0^{-+}}(2481)$. Some fully-strange tetraquark states predicted in theory can be searched for in their dominant fall-apart decay channels in experiment, such as $ϕϕ$, $ϕϕ(1680)$, $η^{(\prime)}ϕ$, $η^{(\prime)}h_1(1415)$, and $ϕf_2^{\prime}(1525)$, to which they have relatively large couplings.

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arXiv2026

Single-quark electromagnetic form factors of charmonium up to $J=2$

We calculate the single-quark electromagnetic form factors of a broad subset of charmonium, including $η_c(1S)$, $η_c(2S)$, $χ_{c0}(1P)$, $χ_{c0}(2P)$, $J/ψ(1S)$, $J/ψ(2S)$, $χ_{c1}(1P)$, $χ_{c1}(2P)$, $h_c(1P)$, $h_c(2P)$, $χ_{c2}(1P)$ and $χ_{c2}(2P)$, via a relativized quark model. The reference frame dependence of the results is estimated as the computational error. We compare our results with those of the lattice quantum chromodynamics (LQCD), the Dyson-Schwinger equation (DSE) and the basis light front quantization (BLFQ) approaches where available and we find that most of our results agree with the other results. We also predict the single-quark electromagnetic form factors of $χ_{c0}(2P)$, $χ_{c1}(2P)$, $h_c(1P)$, $h_c(2P)$, $χ_{c2}(1P)$ and $χ_{c2}(2P)$, where no direct comparisons are available.

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arXiv2025

Decoding spin-parity quantum numbers and decay widths of double $J/ψ$ exotic states

We derive helicity amplitudes for the fully charmed tetraquark states decays into vector meson pair under two types of models, where the one is from quark model and the other one is from diquark model. The decay angular distributions have been given by the cascade decays $T_{4c}\to J/ψ(D_{(s)}^*)+J/ψ(\bar{D}_{(s)}^*)$ along with $J/ψ\to μ^++μ^-$ or $D_{(s)}^*\to D_{(s)}+π$, showing that spin-0 and spin-2 states can be distinguished. We also find that the spin-0 state decay to $J/ψ$-pair exhibits a higher degree of quantum entanglement than that in spin-2 state decays. These findings will assist in experimentally differentiating various spin-parity states, determining decay widths and unveiling undiscovered hadronic states within existing structures, thereby shedding light on the internal properties of double $J/ψ$ exotic states.

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arXiv2025

Production of excited $Λ_c^+$ baryons through $Λ_b$ hadronic weak decays

In this work, to establish a more abundant $Λ_c$ baryon spectrum, we discuss the production potentials of the excited $Λ_c$ baryons through $Λ_b$ hadronic weak decays within a constituent quark model. Based on our successful explanations of the existing experimental data for the $Λ_b \to Λ_c(π^-, K^{-}, D^{-}, D^{-}_s, D_s^{*-})$ processes, we further calculate the decay rates of the $Λ_b$ baryon into the $1P$-, $1D$-, $2S$-, $3S$-, $2P$-, $1F$-, and $2D$-wave $Λ_c$ excited states. It is found that these $Λ_c$ excitations have a large production rate in the $Λ_b$ hadronic weak decay process associated $π^-$ meson emitting, i.e., $Λ_b\to Λ_c^{*}π^-$, their branching fractions can reach up to $\mathcal{O}(10^{-3})$. To search for the higher $3S$-, $2P$-, $1F$-, and $2D$-wave $Λ_c$ states, the $Λ_b \to Λ_c (3S) π^-\to D^{*0}p π^-$, and $Λ_b\to Λ_c(2P,2D,1F) π^-\to D^{(*)0}pπ^-$ decays are worth observing in future experiments.

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arXiv2025

Possible explanations of the observed $Λ_c$ resonances

Inspired by the latest experimental progress, we systematically study the OZI-allowed two-body strong decay properties of $1P$-, $1D$-, $2S$- and $2P$-wave $Λ_c$ baryons within the $j $-$j$ coupling scheme in the framework of the quark pair creation model. The calculations indicate that: (i) Taking the observed states $Λ_c(2595)^+$ and $Λ_c(2625)^+$ as the $1P$-wave $λ$-modes states $Λ_c|J^P=1/2^-,1\rangle_λ$ and $Λ_c|J^P=3/2^-,1\rangle_λ$, respectively, we can reproduce the experimental data well in theory. (ii) Combining with the measured mass and the decay properties of $Λ_c(2860)^+$, this excited state can be explained as $1D$-wave $λ$-mode state $Λ_c|J^P=3/2^+,1\rangle_{λλ}$. (iii) The newly observed state $Λ_c(2910)^+$ may be assigned as one of the $1P$-wave $ρ$-mode states $Λ_c|J^P=3/2^-,2\rangle_ρ$ or $Λ_c|J^P=5/2^-,2\rangle_ρ$. Meanwhile, we notice that the partial decay width ratio between $Σ_cπ$ and $Σ_c^*π$ for the two candidates is significantly different. Hence, experimental progress in this ratio measurement may shed light on the nature of $Λ_c(2910)^+$. (iv) According to the properties of $Λ_c(2765)^+$, we find that the $2S$-wave $λ$-mode state $Λ_{c1}|J^P=1/2^+,0\rangle_λ$ may be a potential candidate. (v) The $2P$-wave $λ$-mode state $Λ_{c1}|J^P=3/2^-,1\rangle_λ$ is mostly likely to be a good assignment of the controversial state $Λ_c(2940)^+$. Both the total decay width and partial decay ratio between $pD^0$ and $Σ_cπ$ are in good agreement with the observations. (vi) In addition, for the missing $Λ_c$ excitations, we obtain their strong decay properties and hope that's useful for future experimental exploration.

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arXiv2025

Bottomonia in an unquenched quark model

The bottomonium spectrum is systematically studied within an unquenched quark model. Based on a good description of both the masses and widths for the well-established states, we further give predictions for the higher $S$-, $P$-, and $D$-wave bottomonium states up to a mass region of $\sim 11.3$ GeV. For the vector states, the $S$-$D$ mixing and dielectron decays are studied. Additionally, to understand the role of the higher vector resonances in the $e^{+}e^{-}$ annihilation reaction, we evaluate the cross section by combining our quark model predictions for the mass, dielectron and strong decay properties. It is found that (i) The mass shifts of the high $b\bar{b}$ states due to the coupled-channel effects are the order of a few tens MeV, most of the high-lying resonances contain significant non-$b\bar{b}$ components. (ii) The $Υ_1(3D,5D,6D)$ states significantly mix with $Υ(4S,6S,7S)$, respectively, which is mainly induced by the intermediate hadronic loops. (iii) The non-$b\bar{b}$ components will lead a significant suppression for the dielectron decay widths of some vector resonances.(iv) The threshold effects of open-bottom meson pairs can cause rich bump structures in the cross section of $e^{+}e^{-}\to b\bar{b}$. Our model shows that the $Υ(10753)$ may arise from threshold effects due to the strong coupling between $Υ(4S)$ and $\bar{B}^*B^*$.

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arXiv2025

Excited $Ω$ hyperon in charmful $Ω_b$ weak decays

We investigate the sextet $b$-baryon decay processes $Ω_b\to J/ψΩ^{(*)}$,where $Ω^*$ represents the $1P$-, $1D$- and $2S$-wave excited $Ω$ hyperons in the spectroscopy. Using the constituent quark model, we obtain ${\cal B}(Ω_b \to J/ψΩ)=8.8\times 10^{-4}$, which agrees with the previous studies to the order of magnitude. By identifying $Ω(2012)$ as $Ω(1^2P_{3/2^-})$, ${\cal B}(Ω_b \to J/ψΩ(2012))=1.1\times 10^{-3}$ can be similarly significant. Additionally, $Ω(1^2D_{5/2^+})$ and $Ω(1^4D_{3/2^+},1^4D_{5/2^+})$ states exhibit production rates of 0.5, and (0.6, 0.8), respectively, relative to their ground-state counterpart. Notably, our findings suggest that ${\cal B}(Ω_b\to J/ψΩ(2^2S_{1/2^+},2^4S_{3/2^+}))$ are as large as $(4.5,20)\times 10^{-4}$, making them accessible to experiments at LHCb.

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arXiv2024

Toward discovering the excited $Ω$ baryons through nonleptonic weak decays of $Ω_c$

The nonleptonic weak decay processes $Ω_c \to Ωπ^+/Ω(1P)π^+/Ω(1D)π^+/Ω(2S)π^+$ are studied using the constituent quark model. The branching fraction of $Ω_c \to Ωπ^+$ is predicted to be $1.0\%$. Considering the newly observed $Ω(2012)$ resonance as a conventional $1P$-wave $Ω$ excite state with spin-parity $J^P=3/2^-$, the newly measured ratio $\mathcal{B}[Ω_c\to Ω(2012)π^+ \to (Ξ\bar{K})^-π^+ ]/\mathcal{B}[Ω_c\to Ωπ^+]$ at Belle can be well understood. Besides, the production rates for the missing $1P-$wave state $Ω(1^2P_{1/2^-})$, two spin quartet $1D-$wave states $Ω(1^4D_{1/2^+})$ and $Ω(1^4D_{3/2^+})$, and two $2S$-wave states $Ω(2^2S_{1/2^+})$ and $Ω(2^4S_{3/2^+})$ are also investigated. It is expected that these missing excited $Ω$ baryons should have large potentials to be discovered through the nonleptonic weak decays of $Ω_c$ in forthcoming experiments by Belle II and/or LHCb.

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arXiv2024

All-heavy pentaquarks

In a nonrelativistic potential quark model framework, we carry out a calculation of the mass spectrum for the low-lying $1S$ all-heavy pentaquark state by adopting the explicitly correlated Gaussian method. The obtained states are compact and lie far above the lowest dissociation baryon-meson threshold. Moreover, using the obtained masses and wave functions we evaluate the fall-apart decay properties within a quark-exchange model. The results show that the $1S$ all-heavy pentaquark states have a fairly narrow fall-apart width, which scatters in the range of $\sim0.1-4.0$ MeV. Their dominant fall-apart decay channels may be ideal for searching for their signals in future experiments.

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arXiv2024

Unified study of nucleon and $Δ$ baryon spectra and their strong decays with chiral dynamics

In this work we systematically study both the mass spectra and strong decays of the nucleon and $Δ$ resonances up to the $N=2$ shell within a unified quark model framework with chiral dynamics. In this framework we achieve a good description of the strong decay properties of the well-established nucleon and $Δ$ resonances. Meanwhile, the mass reversal between $N(1440)1/2^{+}$ as the first radial excitation state and the $1P$-wave nucleon resonances can be explained. We show that the three-body spin-orbit potential arising from the one-gluon exchange can cause a large configuration mixing between $N(1520)3/2^-$ and $N(1700)3/2^-$, and is also responsible for the large splitting between $Δ(1600)1/2^-$ and $Δ(1700)3/2^-$. Some of these baryon resonances turn to weakly couple to the $Nπ$, $Nη$, $KΛ$, and $KΣ$ channels, which may answer the question why they have not been established in these channels via the $πN$ and $γN$ scatterings. It shows that these ``missing resonances" may have large potentials to be established in the $Nππ$ final state due to their large decay rates into either the $Δ(1232)$ or $1P$-wave nucleon resonances via the pionic decays. Further experimental search for their signals in charmonium decays at BESIII is thus strongly recommended.

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arXiv2024

Hidden and double charm-strange tetraquarks and their decays in a potential quark model

We carry out a systematic study of the $1S$-wave hidden and double charm-strange tetraquarks $cs\bar{c}\bar{s}$ and $cc\bar{s}\bar{s}$ in a nonrelativistic potential quark model framework with the explicitly correlated Gaussian method, and the mass spectra, color-spin configurations and possible decay modes are obtained. We find that although these states are all above their open flavor thresholds, their rearrangement decay widths are rather narrow which can be understood by the mismatching of the wave functions between the initial and final states. It implies that the tetraquarks of $cs\bar{c}\bar{s}$ and $cc\bar{s}\bar{s}$ may have a good chance to exist as genuine tetraquark states. It also shows that the color-spin configurations of the $cs\bar{c}\bar{s}$ and $cc\bar{s}\bar{s}$ systems are quite different. We find that for a physical state of $cs\bar{c}\bar{s}$ its color configurations can be dominated by either the $|11\rangle_{c}$ or $|88\rangle_{c}$ ones. It suggests that some hidden charm-strange tetraquark states may strongly couple to two color-singlet hadrons if the kinematics and dynamics allow. In contrast, we find that the color configurations $|11\rangle_{c}$ and $|88\rangle_{c}$ in a double charm-strange $cc\bar{s}\bar{s}$ state are rather compatible. It may suggest that an overall color-singlet tetraquark (i.e. a genuine color-singlet) should always play a role in the $T_{cc\bar{s}\bar{s}}$ states. Discussions taking into account some experimental candidates are presented, and suggestions on further experimental searches are also made.

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arXiv2024

Fully-heavy tetraquark states and their evidences in the LHC observations

Stimulated by the exciting progress on the observations of the fully-charmed tetraquarks at LHC, we carry out a combined analysis of the mass spectra and fall-apart decays of the $1S$-, $2S$-, and $1P$-wave $cc\bar{c}\bar{c}$ states in a nonrelativistic quark model (NRQM). It is found that the $X(6600)$ structure observed in the di-$J/ψ$ invariant mass spectrum can be explained by the $1S$-wave state $T_{(4c)0^{++}}(6550)$. This structure may also bear some feed-down effects from the higher $2S$ and/or $1P$ tetraquark states. The $X(6900)$ structure observed in both the di-$J/ψ$ and $J/ψψ(2S)$ channels can be naturally explained by the $2S$-wave state $T_{(4c)0^{++}}(6957)$. The small shoulder structure around $6.2-6.4$ GeV observed at CMS and ATLAS may be due to the feed-down effects from some $1P$-wave states with $C=-1$ and/or some $2S$-wave states with $J^{PC}=0^{++}$. Other decay channels are implied in such a scenario and they can be investigated by future experimental analyses. Considering the large discovery potential at LHC, we also present predictions for the $bb\bar{b}\bar{b}$ states which can be searched for in the future.

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