arXiv subjects

Xian-Hui Zhong

Publications and source records attributed to Xian-Hui Zhong.

At least 73 records · Page 4Linked to original sources

arXiv2017

Mass spectra and radiative transitions of doubly heavy baryons in a relativized quark model

We study the mass spectra and radiative decays of doubly heavy baryons within the diquark picture in a relativized quark model. The mass of the $J^P=1/2^+$ $Ξ_{cc}$ ground state is predicted to be 3606 MeV, which is consistent with the mass of $Ξ_{cc}^{++}(3621)$ newly observed by the LHCb collaboration. The predicted mass gap between two $S$ wave states, $Ξ_{cc}^*$ ($J^P=3/2^+$) and $Ξ_{cc}$ ($J^P=1/2^+$), is 69 MeV. Furthermore, the radiative transitions of doubly heavy baryons are also estimated by using the realistic wave functions obtained from relativized quark model. The radiative decay widths of $Ξ_{cc}^{*++} \to Ξ_{cc}^{++}γ$ and $Ξ_{cc}^{*+} \to Ξ_{cc}^+γ$ are predicted to be about 7 and 4 keV, respectively. These predictions of doubly heavy baryons can provide helpful information for future experimental searches.

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arXiv2017

Strong and radiative decays of the doubly charmed baryons

We have systematically studied the strong and radiative decays of the low-lying $1P$-wave doubly charmed baryons. Some interesting observations are: (i) The states $Ξ_{cc}^*$ and $Ω_{cc}^*$ with $J^P=3/2^+$ have a fairly large decay rate into the $Ξ_{cc}γ$ and $Ω_{cc}γ$ channels with a width $\sim 15$ and $\sim7$ keV, respectively. (ii) The lowest lying excited doubly charmed baryons are dominated by the $1P$ $ρ$ mode excitations, which should be quite narrow states. They decay into the ground state with $J^P=1/2^+$ through the radiative transitions with a significant ratio. (iii) The total decay widths of the first orbital excitations of $λ$ mode ($1P_λ$ states with $J^P=1/2^-$, $3/2^-$, $5/2^-$) are about $Γ\sim100$ MeV, and the ratio between the radiative and hadronic decay widths is about $\mathcal{O}(10^{-3})$.

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arXiv2017

Understanding the newly observed $Ω_c$ states through their decays

The strong and radiative decay properties of the low-lying $Ω_c$ states are studied in a constituent quark model. We find that the newly observed $Ω_c$ states by the LHCb Collaboration can fit in well the decay patterns. Thus, their spin-parity can be possibly assigned as the following: (i) The $Ω_c(3000)$ has $J^P=1/2^-$ and corresponds to the narrow $1P$ mixed state $|1^2P_λ\frac{1}{2}^-\rangle_1$, its partner $|1^2P_λ\frac{1}{2}^-\rangle_2$ should be a broad state with a width of $\sim 100$ MeV. (ii) The $Ω_c(3050)$ and $Ω_c(3066)$ can be assigned to be two $J^P=3/2^-$ states, $|1^4P_λ\frac{3}{2}^-\rangle$ and $|1^2P_λ\frac{3}{2}^-\rangle$, respectively. (iii) The $Ω_c(3090)$ can be assigned as the $|1^4P_λ\frac{5}{2}^-\rangle$ state with $J^P=5/2^-$. (iv) The $Ω_c(3119)$ might correspond to one of the two $2S$ states of the first radial excitations, i.e. $|2^2S_{λλ}\frac{1}{2}^+\rangle$ or $|2^4S_{λλ}\frac{3}{2}^+\rangle$.

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arXiv2017

Spectrum and electromagnetic transitions of bottomonium

Stimulated by the exciting progress in the observation of new bottomonium states, we study the bottomonium spectrum. To calculate the mass spectrum, we adopt a nonrelativistic screened potential model. The radial Schrödinger equation is solved with the three-point difference central method, where the spin-dependent potentials are dealt with non-perturbatively. With this treatment, the corrections of the spin-dependent potentials to the wave functions can be included successfully. Furthermore, we calculate the electromagnetic transitions of the $nS$ ($n\leq 4$), $nP$ ($n\leq 3$), and $nD$ ($n\leq 2$) bottomonium states with a nonrelativistic electromagnetic transition operator widely applied to meson photoproduction reactions. Our predicted masses, hyperfine and fine splittings, electromagnetic transition widths and branching ratios of the bottomonium states are in good agreement with the available experimental data. Especially, the EM transitions of $Υ(3S)\to χ_{b1,2}(1P)γ$, which were not well understood in previous studies, can be reasonably explained by considering the corrections of the spin-dependent interactions to the wave functions. We also discuss the observations of the missing bottomonium states by using radiative transitions. Some important radiative decay chains involving the missing bottomonium states are suggested to be observed. We hope our study can provide some useful references to observe and measure the properties of bottomonium mesons in forthcoming experiments.

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arXiv2017

Quark model study of the $πN\to πN$ reactions up to the $N(1440)$ resonance region

A combined analysis of the reactions $π^+p\to π^+p$, $π^-p\to π^-p$ and $π^-p\to π^0n$ is carried out with a chiral quark model. The observations are reasonably described from the $Δ(1232)$ resonance region up to the $N(1440)$ resonance region. Besides the $Δ(1232)P_{33}$, a confirmed role of $N(1440)P_{11}$ is found in the polarizations of the $π^-p\to π^-p$ and $π^-p\toπ^0n$ reactions. It is found that the $N(1440)Nπ$ and $Δ(1232)Nπ$ couplings are about $1.7$ and $4.8$ times larger than the expectations from the simple quark model, respectively, which may suggest the unusual property of $N(1440)P_{11}$ and deficiency of the simple quark model in the description of $N(1440)P_{11}$ and $Δ(1232)P_{33}$. The $t$- and $u$-channel backgrounds have notable contributions to the $π^+ p\rightarrowπ^+ p$ reaction, while in the $π^-p\rightarrow π^- p,π^0 n$ reactions, the $s$-channel nucleon and $t$- and $u$-channel backgrounds play crucial roles.

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arXiv2016

Charmonium spectrum and their electromagnetic transitions with higher multipole contributions

The charmonium spectrum is calculated with two nonrelativistic quark models, the linear potential model and the screened potential model. Using the obtained wavefunctions, we evaluate the electromagnetic transitions of charmonium states up to $4S$ multiplet. The higher multipole contributions are included by a multipole expansion of the electromagnetic interactions. Our results are in reasonable agreement with the measurements. As conventional charmonium states, the radiative decay properties of the newly observed charmonium-like states, such as $X(3823)$, $X(3872)$, $X(4140/4274)$, are discussed. The $X(3823)$ as $ψ_2(1D)$, its radiative decay properties well agree with the observations. From the radiative decay properties of $X(3872)$, one can not exclude it as a $χ_{c1}(2P)$ dominant state. We also give discussions of possibly observing the missing charmonium states in radiative transitions, which might provide some useful references to look for them in forthcoming experiments. The higher multipole contributions to the electromagnetic transitions are analyzed as well. It is found that the higher contribution from the magnetic part could give notable corrections to some E1 dominant processes by interfering with the E1 amplitudes. Our predictions for the normalized magnetic quadrupole amplitudes $M_2$ of the $χ_{c1,2}(1P)\to J/ψγ$ processes are in good agreement with the recent CLEO measurements.

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arXiv2016

Combined analysis of the $π^-p\rightarrow K^0Λ$, $ηn$ reactions in a chiral quark model

A combined analysis of the reactions $π^-p\rightarrow K^0Λ$ and $ηn$ is carried out with a chiral quark model. The data in the center-of-mass (c.m.) energy range from threshold up to $W\simeq 1.8$ GeV are reasonably described. For $π^-p\rightarrow K^0Λ$, it is found that $N(1535)S_{11}$ and $N(1650)S_{11}$ paly crucial roles near threshold. The $N(1650)S_{11}$ resonance contributes to the reaction through configuration mixing with $N(1535)S_{11}$. The constructive interference between $N(1535)S_{11}$ and $N(1650)S_{11}$ is responsible for the peak structure around threshold in the total cross section. The $n$-pole, $u$- and $t$-channel backgrounds provide significant contributions to the reaction as well. While, for the $π^-p\rightarrow ηn$ process, the "first peak" in the total cross section is dominant by $N(1535)S_{11}$, which has a sizeable destructive interference with $N(1650)S_{11}$. Around $P_π\simeq $ 1.0 GeV/c ($W\simeq 1.7$ GeV), there seems to be a small bump structure in the total cross section, which might be explained by the interference between the $u$-channel and $N(1650)S_{11}$. The $N(1520)D_{13}$ resonance notably affects the angle distributions of the cross sections, although less effects are seen in the total cross section. The role of $P$-wave state $N(1720)P_{13}$ should be further confirmed by future experiments. If $N(1720)P_{13}$ has a narrow width of $Γ\simeq 120$ MeV as found in our previous work by a study of the $π^0$ photoproduction processes, obvious evidence should be seen in the $π^-p\rightarrow K^0Λ$ and $ηn$ processes as well.

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arXiv2016

Radiative transitions of charmonium states in a constituent quark model

We study the electromagnetic (EM) transitions of the $nS$, $nP$ ($n\leq 3$), and $nD$ ($n\leq 2$) charmonium states with a constituent quark model. We obtain a reasonable description of the EM transitions of the well-established charmonium states $J/ψ$, $ψ(2S)$, $χ_{cJ}(1P)$, $h_c(1P)$ and $ψ(3770)$. We find that the M2 transitions give notable corrections to some E1 dominant processes by interfering with the E1 transitions. Our predictions of EM decay properties for the higher charmonium states are also presented and compared with other model predictions. In particular, we discuss the EM decay properties of some $"XYZ"$ states, such as $X(3823)$, $X(3872)$, $X(3915)$, $X(3940)$ and $X(4350)$ as conventional charmonium states. Assuming $X(3872)$ as the $χ_{c1}(2P)$ state, our predicted ratio $Γ[X(3872)\to ψ(2S)γ]/Γ[X(3872)\to J/ψγ]\simeq 4.0$ is consistent with BaBar's measurement.

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arXiv2015

Neutral pion photoproduction on the nucleon in a chiral quark model

A chiral quark-model approach is adopted to study the $γp\rightarrow π^0p$ and $γn\rightarrow π^0 n$ reactions. Good descriptions of the total and differential cross sections and single-polarization observables are obtained from the pion production threshold up to the second resonance region. It is found that (i) the $n=0$ shell resonance $Δ(1232)P_{33}$, the $n=1$ shell resonances $N(1535)S_{11}$ and $N(1520)D_{13}$, and the $n=2$ shell resonance $N(1720)P_{13}$ play crucial roles in these two processes. They are responsible for the first, second and third bump structures in the cross sections, respectively. (ii) Furthermore, obvious evidences of $N(1650)S_{11}$ and $Δ(1620)S_{31}$ are also found in the reactions. They notably affect the cross sections and the polarization observables from the second resonance region to the third resonance region. (iii) The $u$-channel background plays a crucial role in the reactions. It has strong interferences with the $s$-channel resonances. (iv) The $t$-channel background seems to be needed in the reactions. Including the $t$-channel vector-meson exchange contribution, the descriptions in the energy region $E_γ= 600\sim 900$ MeV are improved significantly. The helicity amplitudes of the main resonances, $Δ(1232)P_{33}$, $N(1535)S_{11}$, $N(1520)D_{13}$, $N(1720)P_{13}$, $N(1650)S_{11}$ and $Δ(1620)S_{31}$, are extracted and compared with the results from other groups.

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arXiv2015

Role of $Λ(1670)$ in the $γp \to K^+ ηΛ$ reaction near threshold

The role of the $Λ(1670)$ resonance in the $γp \to K^+ ηΛ$ reaction near threshold is studied within an effective Lagrangian approach. We perform a calculation for the total and differential cross section of the $γp \to K^+ ηΛ$ reaction by including the contributions from the $Λ(1670)$ intermediate state decaying into $ηΛ$ dominated by $K^-$ and $K^{*-}$ mesons exchanges, the nucleon pole and $N^*(1535)$ resonance decaying into $K^+ Λ$ dominated by exchanges of $ω$ and $K^-$ mesons. Besides, the non-resonance process and contact terms to keep the total scattering amplitude gauge invariant are also considered. With our model parameters, the total cross section of this reaction is of the order of $1$ nanobarn at photon beam energy $E_γ \sim 2.5$ GeV. It is expected that our model predictions could be tested by future experiments.

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arXiv2014

Strong decays of higher excited heavy-light mesons in a chiral quark model

The strong decay properties of the higher excited heavy-light mesons from the first radially excited states up to the first $F$-wave states are studied in a constituent quark model. It is found many missing excitations have good potentials to be found in future experiments for their narrow widths, some of them dominantly decay into the first orbital excitations rather than into ground states. In future observations, one should focus on the decay processes not only into the ground states, but also into the low-lying $P$-wave excitations with $J^P=0^+,1^+$. Furthermore, the nature of the newly observed states $D_J(3000)$, $D_J^*(3000)$ and B(5970) is discussed. It is predicted that $D_J(3000)$ seems to be a partner of $D_{sJ}(3040)$, which could be identified as the high-mass mixed state $|2{P_1}>_L$ ($J^P=1^+$) via the $2^1P_1$-$2^3P_1$ mixing. The $D_J^*(3000)$ resonance seems to favor the $1^3F_4$ state, however, the quantum numbers $J^P=0^+$ and $2^+$ can not be excluded complectly, more experimental observations are needed to determine its $J^P$ values. The B(5970) resonance is most likely to be the $1^3D_3$ with $J^P=3^-$.

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arXiv2013

Low energy reactions $K^-p\rightarrowΣ^0π^0$, $Λπ^0$, $\bar{K}^0n$ and the strangeness $S=-1$ hyperons

A combined study of the reactions $K^-p\rightarrow Σ^0π^0$, $Λπ^0$ and $\bar{K}^0n$ at low energies is carried out with a chiral quark-model approach. Good descriptions of the experimental observations are obtained. The roles of the low-lying strangeness $S=-1$ hyperon resonances in these processes are carefully analyzed. We find that: (i) In the $K^-p\rightarrow Σ^0π^0$ process, both $Λ(1405)S_{01}$ and $Λ(1520)D_{03}$ play dominant roles. Significant contributions of $Λ(1670)S_{01}$ and $Λ(1690)D_{03}$ could be seen around their threshold; (ii) In the $K^-p\rightarrow Λπ^0$ process, some obvious evidence of $Σ(1775)D_{15}$ and $Σ(1750)S_{11}$ could be found. Some hints of $Σ(1620)S_{11}$ might exist in the reaction as well. $Σ(1750)S_{11}$ and $Σ(1620)S_{11}$ should correspond to the representations $[70,^48]S_{11}$ and $[70,^28]S_{11}$, respectively; (iii) In the $K^-p\rightarrow \bar{K}^0n$ process, the dominant resonances are $Λ(1405)$ and $Λ(1520)$. Some evidence of $Λ(1690)D_{03}$, $Σ(1670)D_{13}$ and $Σ(1775)D_{15}$ could be seen as well. A weak coupling of $Λ(1670)S_{01}$ to $\bar{K}N$ should be needed in the reactions $K^-p\rightarrow Σ^0π^0$ and $\bar{K}^0n$. Furthermore, by analyzing these reactions, we also find that the $u$-, t-channel backgrounds and s-channel Born term play crucial roles in the reactions.

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arXiv2013

Low energy reaction $K^-p\rightarrowΛη$ and the negative parity $Λ$ resonances

The reaction $K^-p\rightarrowΛη$ at low energies is studied with a chiral quark model approach. Good descriptions of the existing experimental data are obtained. It is found that $Λ(1670)$ dominates the reaction around threshold. Furthermore, $u$- and $t$-channel backgrounds play crucial roles in this reaction as well. The contributions from the $D$-wave state $Λ(1690)$ are negligibly small for its tiny coupling to $ηΛ$. To understand the strong coupling properties of the low-lying negative parity $Λ$ resonances extracted from the $\bar{K}N$ scattering, we further study their strong decays. It is found that these resonances are most likely mixed states between different configurations. Considering these low-lying negative parity $Λ$ resonances as mixed three-quark states, we can reasonably understand both their strong decay properties from Particle Data Group and their strong coupling properties extracted from the $\bar{K}N$ scattering. As a byproduct, we also predict the strong decay properties of the missing $D$-wave state $|Λ\frac{3}{2}^-\ >_3$ with a mass of $\sim1.8$ GeV. We suggest our experimental colleagues search it in the $Σ(1385)π$ and $Σπ$ channels.

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arXiv2013

$Ξ$ baryon strong decays in a chiral quark model

The strong decays of $Ξ$ baryons up to N=2 shell were studied in a chiral quark model. The strong decay properties of these well-established ground decuplet baryons were reasonably described. We found that (i) $Ξ(1690)$ and $Ξ(1820)$ could be assigned to the spin-parity $J^P=1/2^-$ state $|70,^{2}{8},1,1,1/2^->$ and the spin-parity $J^P=3/2^-$ state $|70,^{2}{8},1,1,3/2^->$, respectively. Slight configuration mixing might exist in these two negative parity states. (ii) $Ξ(1950)$ might correspond to several different $Ξ$ resonances. The broad states ($Γ\sim 100$ MeV) observed in the $Ξπ$ channel could be classified as the pure $J^P=5/2^-$ octet state $Ξ^0|70,^{4}8,1,1,5/2^->$ or the mixed state $|Ξ1/2^->_3 $ with $J^P=1/2^-$. The $Ξ$ resonances with moderate width ($Γ\sim 60$ MeV) observed in the $Ξπ$ channel might correspond to the $J^P=1/2^+$ excitation $|56,^{4}10,2,2,1/2^+>$. The second orbital excitation $|56,^{4}10,2,2,3/2^+>$ and the mixed state $|Ξ1/2^->_1$ might be candidates for the narrow width state observed in the $Λ\bar{K}$ channel, however, their spin-parity numbers are incompatible with the moment analysis of the data. (iii) $Ξ(2030)$ could not be assigned to either any spin-parity $J^P=7/2^+$ states or any pure $J^P=5/2^+$ configurations. It seems to favor the $|70,^{2}8,2,2,3/2^+>$ assignment, however, its spin conflicts with the moment analysis of the data. To find more $Ξ$ resonances, the observations in the $Ξ(1530)π$ and $Σ(1385) \bar{K}$ channels are necessary.

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arXiv2012

Charm-strange baryon strong decays in a chiral quark model

The strong decays of charm-strange baryons up to N=2 shell are studied in a chiral quark model. The theoretical predictions for the well determined charm-strange baryons, $Ξ_c^*(2645)$, $Ξ_c(2790)$ and $Ξ_c(2815)$, are in good agreement with the experimental data. This model is also extended to analyze the strong decays of the other newly observed charm-strange baryons $Ξ_c(2930)$, $Ξ_c(2980)$, $Ξ_c(3055)$, $Ξ_c(3080)$ and $Ξ_c(3123)$. Our predictions are given as follows. (i) $Ξ_c(2930)$ might be the first $P$-wave excitation of $Ξ_c'$ with $J^P=1/2^-$, favors the $|Ξ_c'\ ^2P_λ1/2^->$ or $|Ξ_c'\ ^4P_λ1/2^->$ state. (ii) $Ξ_c(2980)$ might correspond to two overlapping $P$-wave states $|Ξ_c'\ ^2P_ρ1/2^->$ and $|Ξ_c'\ ^2P_ρ3/2^->$, respectively. The $Ξ_c(2980)$ observed in the $Λ_c^+\bar{K}π$ final state is most likely to be the $|Ξ_c'\ ^2P_ρ1/2^->$ state, while the narrower resonance with a mass $m\simeq 2.97$ GeV observed in the $Ξ_c^*(2645)π$ channel favors to be assigned to the $|Ξ_c'\ ^2P_ρ3/2^->$ state. (iii) $Ξ_c(3080)$ favors to be classified as the $|Ξ_c\ S_{ρρ} 1/2^+>$ state, i.e., the first radial excitation (2S) of $Ξ_c$. (iv) $Ξ_c(3055)$ is most likely to be the first $D$-wave excitation of $Ξ_c$ with $J^P=3/2^+$, favors the $|Ξ_c\ ^2D_{λλ} 3/2^+>$ state. (v) $Ξ_c(3123)$ might be assigned to the $|Ξ_c'\ ^4D_{λλ} 3/2^+>$, $|Ξ_c'\ ^4D_{λλ} 5/2^+>$, or $|Ξ_c\ ^2D_{ρρ} 5/2^+>$ state. As a by-product, we calculate the strong decays of the bottom baryons $Σ_b^{\pm}$, $Σ_b^{*\pm}$ and $Ξ_b^*$, which are in good agreement with the recent observations as well.

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arXiv2011

$η'$ photoproduction on the nucleons in the quark model

A chiral quark-model approach is adopted to study the $γp\rightarrow η'p$ and $γn\rightarrow η' n$. Good descriptions of the recent observations from CLAS and CBELSA/TAPS are obtained. Both of the processes are governed by $S_{11}(1535)$ and $u$ channel background. Strong evidence of an $n=3$ shell resonance $D_{15}(2080)$ is found in the reactions, which accounts for the bump-like structure around $W=2.1$ GeV observed in the total cross section and excitation functions at very forward angles. The $S_{11}(1920)$ seems to be needed in the reactions, with which the total cross section near threshold for the $γp\rightarrow η' p$ is improved slightly. The polarized beam asymmetries show some sensitivities to $D_{13}(1520)$, although its effects on the differential cross sections and total cross sections are negligible. There is no obvious evidence of the $P$-, $D_{13}$-, $F$- and $G$-wave resonances with a mass around 2.0 GeV in the reactions.

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arXiv2011

$η$ photoproduction on the quasi-free nucleons in the chiral quark model

A chiral quark-model approach is adopted to study the $η$ photoproduction off the quasi-free neutron and proton from a deuteron target. Good descriptions of the differential cross sections, total cross sections and beam asymmetries for these two processes are obtained in the low energy region. For $γp\rightarrow ηp$, the dominant resonances are $S_{11}(1535)$, $S_{11}(1650)$, $D_{13}(1520)$, $D_{13}(1700)$ and $P_{13}(1720)$. While for the $γn\rightarrow ηn$ process, the dominant resonances are $S_{11}(1535)$, $S_{11}(1650)$, $D_{13}(1520)$, $D_{15}(1675)$ and $P_{13}(1720)$. Furthermore, the $u$ channel backgrounds have significant contributions to the $η$ photoproduction processes. The configuration mixings in the $S_{11}(1535,1650)$ and $D_{13}(1520,1700)$ can be extracted, i.e. $θ_S\simeq 26^\circ$ and $θ_D\simeq 21^\circ$. It shows that the narrow bump-like structure around $W= 1.68$ GeV observed in $γn\rightarrow ηn$ can be naturally explained by the constructive interferences between $S_{11}(1535)$ and $S_{11}(1650)$. In contrast, the destructive interference between $S_{11}(1535)$ and $S_{11}(1650)$ produces the shallow dip around $W= 1.67$ GeV in $γp\rightarrow ηp$. The $S$ wave interfering behaviors in the proton and neutron reactions are correlated with each other in the quark model framework, and no new exotic nucleon resonances are needed in these two reactions.

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arXiv2010

Strong decays of the newly observed $D(2550)$, $D(2600)$, $D(2750)$, and $D(2760)$

The strong decay properties of the newly observed $D(2550)$, $D(2600)$, $D(2750)$ and $D(2760)$ are studied in a constituent quark model. It is predicted that the $D(2760)$ and $D(2750)$ seem to be two overlapping resonances. The $D(2760)$ could be identified as the $1^3D_3$ with $J^P=3^-$, while the $D(2750)$ is most likely to be the high-mass mixed state $|1{D_2}'>_H$ ($J^P=2^-$) via the $1^1D_2$-$1^3D_2$ mixing. The $D(2600)$ favors the low-mass mixed state $|(SD)_1>_L$ $(J^P=1^-)$ via the $1^3D_1$-$2^3S_1$ mixing. The $D(2550)$ as the $2^1S_0$ assignment bears controversies for its too broad width given in experiments.

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