arXiv subjects

Ju-Jun Xie

Publications and source records attributed to Ju-Jun Xie.

At least 73 records · Page 4Linked to original sources

arXiv2023

The quark orbital angular momentum of ground state octet baryons

Here we study the quark orbital angular momentum of the ground octet baryons employing an extended chiral constituent quark model, within which the baryon wave functions are taken to be superposition of the traditional $qqq$ and the $qqqq\bar{q}$ higher Fock components. Coupling between the two configurations is estimated using the $^3P_{0}$ quark-antiquark creation mechanism, and the corresponding coupling strength is determined by fitting the sea flavor asymmetry of the nucleon. The obtained numerical results show that the quark angular momentum of the nucleon, $Σ$, $Λ$ and $Ξ$ hyperons are in the range $0.10$-$0.30$. In addition, the quark angular momentum of all the hyperons are a little bit smaller than that of the nucleon. And the octet baryons spin fractions taken by the intrinsic quark orbital angular momentum could be up to $60\%$ in present model.

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arXiv2023

The $Σ$ and $Ξ$ electromagnetic form factors in the extended vector meson dominance model

We propose a phenomenological extended vector meson dominance model for the baryon electromagnetic structure, and it is found that the current experimental data on the $Σ$ and $Ξ$ electromagnetic form factors in the time-like region can be well described. Meanwhile, we can also reproduce the ratios of the total cross sections of reactions $e^+e^- \to Σ^+\barΣ^-$, $Σ^0\barΣ^0$, and $Σ^-\barΣ^+$, which are $9.7 \pm 1.3 : 3.3 \pm 0.7 :1$ at center-of-mass energies from $2.3864$ to $3.02$ GeV. We also analytically continue the expression of the form factors to space-like region and estimate the charge radii of the $Σ$ and $Ξ$ hyperons. The result for the $Σ^-$ is in agreement with the experimental date.

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arXiv2022

Spectrum of the S-wave fully-heavy tetraquark states

In present work, spectrum of the $S$-wave fully-heavy tetraquark states $QQ\bar{Q}\bar{Q}$ ($Q=c,b$), i.e., $cc\bar{c}\bar{c}$, $bb\bar{b}\bar{b}$, $cc\bar{b}\bar{b}$/$bb\bar{c}\bar{c}$, $bc\bar{c}\bar{c}$/ $cc\bar{b}\bar{c}$, $bb\bar{c}\bar{b}$/$cb\bar{b}\bar{b}$, and $bc\bar{b}\bar{c}$ are systematically investigated within an nonrelativistic constituent quark model, in which the Instanton-induced and one-gluon-exchange interactions are taken into account as the residual spin-dependent hyperfine interaction. Our results show that the states with $cc\bar{c}\bar{c}$ and $bb\bar{b}\bar{b}$ components could be located around $ 6500$ MeV and $ 19200$ MeV, respectively. Based on our calculations, the new $X(6900)$ state observed by LHCb may be not a ground $cc\bar{c}\bar{c}$ tetraquark state, while it could be an orbitally or radially excited state of $cc\bar{c}\bar{c}$ system. On the other hand, the recently reported $X(6600)$ state by CMS and ATLAS can be explained as a ground $cc\bar{c}\bar{c}$ tetraquark state with spin-parity $J^{PC} =0^{++}$.

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arXiv2022

Production of $D^_{s0}(2317)$ and $D_{s1}(2460)$ in $B$ decays as $D^{()}K$ and $D^{(*)}_sη$ molecules

The molecular nature of $D_{s0}^{\ast}(2317)$ and $D_{s1}(2460)$ have been extensively studied from the perspective of their masses, decay properties, and production rates. In this work, we study the weak decays of $B \to \bar{D}^{(\ast)}D_{s0}^{*}(2317)$ and $B \to \bar{D}^{(\ast)}D_{s1}(2460)$ by invoking triangle diagrams where the $B$ meson first decays weakly into $\bar{D}^{(\ast)}D_{s}^{(\ast)}$ and $J/ψK$($η_{c}K$), and then the $D_{s0}^{\ast}(2317)$ and $D_{s1}(2460)$ are dynamically generated by the final-state interactions of $D_{s}^{(\ast)}η$ and $D^{(\ast)}K$ via exchanges of $η$ and $D^{(\ast)}$ mesons. The obtained absolute branching fractions of Br$[B \to \bar{D}^{(\ast)}D_{s0}^{*}(2317)]$ are in reasonable agreement with the experimental data, while the branching fractions of Br$[B \to \bar{D}^{(\ast)}D_{s1}(2460)]$ are smaller than the experimental central values by almost a factor of two to three. We tentatively attribute such a discrepancy to either reaction mechanisms missing in the present work or the likely existence of a relatively larger $c\bar{s}$ component in the $D_{s1}(2460)$ wave function.

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arXiv2022

Nature of $X(3872)$ in $B^0 \to K^0 X(3872)$ and $B^+ \to K^+ X(3872)$ decays

We investigate the decays of $B^0 \to K^0 X(3872)$ and $B^+ \to K^+ X(3872)$ based on the picture where the $X(3872)$ resonance is strongly coupled to the $D\bar{D}^* + c.c.$ channel. In addition to the decay mechanism where the $X(3872)$ resonance is formed from the $c\bar{c}$ pair hadronization with the short-distance interaction, we have also considered the $D\bar{D}^*$ rescattering diagrams in the long-distance scale, where $D$ and $\bar{D}^*$ are formed from $c$ and $\bar{c}$ separately. Because of the difference of the mass thresholds of charged and neutral $D\bar{D}^*$ channels, and the rather narrow width of the $X(3872)$ resonance, at the $X(3872)$ mass, the loop functions of $D^0\bar{D}^{*0}$ and $D^+\bar{D}^{*-}$ are much different. Taking this difference into account, the ratio of $\mathcal{B}[B^0\to K^0X(3872)]/\mathcal{B}[B^+ \to K^+ X(3872)] \simeq 0.5$ can be naturally obtained. Based on this result, we also evaluate the decay widths of $B_s^0 \to η(η') X(3872)$. It is expected that future experimental measurements of these decays can be used to elucidate the nature of the $X(3872)$ resonance.

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arXiv2022

Faddeev fixed-center approximation to the $ηK^\bar{K}^$, $πK^\bar{K}^$ and $KK^\bar{K}^$ systems

The three-body $ηK^*\bar{K}^*$, $πK^*\bar{K}^*$ and $KK^*\bar{K}^*$ systems are investigated within the framework of fixed-center approximation to the Faddeev equations, where $K^*\bar{K}^*$ is treated as the scalar meson $f_0(1710)$. The interactions between $π$, $η$, $K$ and $K^*$ are taking from the chiral unitary approach. By scattering the $η$ meson on the clusterized $(K^*\bar{K}^*)_{f_0(1710)}$ system, we find a peak in the modulus squared of the three-body scattering amplitude and it can be associated as a bound state with quantum numbers $I^G(J^{PC})=0^+(0^{-+})$. Its mass and width are around 2054 MeV and 60 MeV, respectively. This state could be associated to the $η(2100)$ meson. For the $π(K^*\bar{K}^*)_{f_0(1710)}$ scattering, we find a bump structure around 1900-2000 MeV with quantum numbers $1^-({0^{-+}})$. While for the $K K^* \bar{K}^*)_{f_0(1710)}$ system, there are three structures. One of them is much stable and its mass is about 2130 MeV. It is expected that these theoretical predictions here could be tested by future experimental measurements, such as by the BESIII, BelleII and LHCb collaborations.

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arXiv2022

Further understanding the nature of $a_0(1710)$ in the $D^+_s \to π^0 K^+ K^0_S$ decay

Based on our previous work about the role of $a_0(1710)$ in the $D_s^+\toπ^+K_S^0K_S^0$ decay [Phy. Rev. D 105, 116010 (2022)], we perform a further theoretical study of $a_0(1710)^+$ in the process $D^+_s \to π^0 a_0(1710)^+ \to π^0 K^+ K^0_S$. In addition to $a_0(1710)$, the contributions of $K^*$ and $a_0(980)$ are also taken into account. Firstly, we consider the contributions from the tree diagrams of $K^{*+} \to K^+π^0$ and $\bar{K}^{*0} \to π^0 \bar{K}^0$. Secondly, we describe the final state interaction of $K\bar{K}$ in the chiral unitary approach to study the contribution of $a_0(980)$, while the $a_0(1710)$ state is dynamically generated from the $K^*\bar{K}^*$ interaction, and then decays into $K^+\bar{K}^0$. Since the final $K^+ K_S^0$ state is in pure isospin $I=1$, the $D_s^+\toπ^0K^+K_s^0$ decay is an ideal process to study the $a_0(1710)^+$ and $a_0(980)^+$ resonances. Based on our theoretical calculations, it is found that the recent experimental measurements on the $K^+K^0_S$, $π^0K^+$, and $π^0 K_S^0$ invariant mass distributions can be well reproduced, which supports the molecular $K^*\bar{K}^*$ nature of the scalar $a_0(1710)$ resonance.

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arXiv2022

Radiative decays of the neutral $Z_c(3900)$ and $Z_c(4020)$

We study the radiative decays $Z_c(3900)/Z_c(4020) \to γχ_{cJ}(γχ_{cJ}^\prime)$ ($J=0, 1, 2$), with the assumption that the $Z_c(3900)$ and $Z_c(4020)$ couple strongly to $D\bar D^* +c.c$ and $D^*{\bar D}^*$ channel, respectively. By considering the contributions of intermediate charmed mesons triangle loops within an effective Lagrangian approach, it is shown that the calculated partial widths of $Z_c(3900) \to γχ_{cJ}$ are about a few hundreds keVs, while the obtained partial widths $Z_c(4020) \to γχ_{cJ}$ are about tens of keVs. The predicted partial widths of $Z_c(3900)\toγχ_{c0,1}^\prime$ are less than 1 keV, which mainly due to the very small phase space. For $Z_c(4020)\toγχ_{c0,2}^\prime$, the calculated partial widths are usually smaller than 1 keV. For the $Z_c(4020)\toγχ_{c1}^\prime$ process, the obtained partial widths can reach up to the order of 10 keV. Furthermore, the dependence of these ratios between different decay modes on the masses of $Z_c(3900)$ or $Z_c(4020)$ are also investigated, which may be a good quantity for the experiments. It is hoped that these calculations here could be tested by future experiments.

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arXiv2022

Investigations on the charmless decays of $X(3872)$ in intermediate meson loops model

The charmless decay processes of $X(3872)$ provide us a good platform to study the nature and the decay mechanism of $X(3872)$. Based on a molecular nature of $X(3872)$ as a $\bar{D}D^*$ bound state, we have investigated the charmless decays $X(3872) \to VV$ and $VP$ via intermediate $D^*{\bar D} +c.c.$ meson loops, where $V$ and $P$ stand for light vector and pseudoscalar mesons, respectively. We discuss three cases, i.e., pure neutral components ($θ=0$), isospin singlet ($θ=π/4$) and neutral components dominant ($θ= π/6$), where $θ$ is a phase angle describing the proportion of neutral and charged constituents. The proportion of neutral and charged constituent have an influence on the decay widths of $X(3872) \to VV$ and $VP$. With the coupling constant of $X(3872)$ to the $\bar{D}D^*$ channel obtained under the molecule ansatz of $X(3872)$ resonance, the predicted decay widths of $X(3872)\rightarrow VV$ are about tens of keVs, while the decay width can reach a few hundreds of keVs for $X(3872)\to VP$. The dependence of these ratios between different decay modes of $X(3872)\to VV$ and $X(3872)\to VP$ to the mixing angle $θ$ is also investigated. It is expected that the theoretical calculations here can be tested by future experiments.

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arXiv2022

Further understanding the nature of $Ω(2012)$ within a chiral quark model

In our previous works, we have analyzed the two-body strong decays of the low-lying $Ω$ baryon states within a chiral quark model. The results show that the $Ω(2012)$ resonance favors the three-quark state with $J^P=3/2^-$ classified in the quark model. With this assignment, in the present work we further study the three-body strong decay $Ω(2012)\to Ξ^*(1530)\bar{K} \to Ξπ\bar{K}$ and coupled-channel effects on $Ω(2012)$ from nearby channels $Ξ\bar{K}$, $Ωη$ and $Ξ^*(1530)\bar{K}$ within the chiral quark model as well. It is found that the $Ω(2012)$ resonance has a sizeable decay rate into the three-body final state $Ξπ\bar{K}$. The predicted ratio $R_{Ξ\bar{K}}^{Ξπ\bar{K}}=\mathcal{B}[Ω(2012)\to Ξ^*(1530)\bar{K}\to Ξπ\bar{K}]/\mathcal{B}[Ω(2012)\to Ξ\bar{K}]\simeq 12\%$ is close to the up limit $11\%$ measured by the Belle Collaboration in 2019, however, our predicted ratio is too small to be comparable with the recent data $0.97\pm 0.31$. Furthermore, our results show that the coupled-channel effects on the $Ω(2012)$ is not large, its components should be dominated by the bare three-quark state, while the proportion of the molecular components is only $\sim 16\%$. To clarify the nature of $Ω(2012)$, the ratio $R_{Ξ\bar{K}}^{Ξπ\bar{K}}$ is expected to be tested by other experiments.

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arXiv2022

The low-lying hidden- and double-charm tetraquark states in a constituent quark model with Instanton-induced Interaction

Spectrum of the low-lying hidden- and double-charm tetraquark states are investigated in a nonrelativistic quark potential model, where the Instanton-induced interaction is taken as the residual spin-dependent hyperfine interaction between quarks. The model parameters are fixed by fitting the spectrum of the ground hadron states. Our numerical results show that masses of several presently studied tetraquark states are close to those of the experimentally observed candidates of exotic meson, which indicates that the corresponding compact tetraquark components may take considerable probabilities in those observed exotic states.

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arXiv2022

Theoretical study on the contributions of $ω$ meson to the $X(3872) \to J/ψπ^+π^-$ and $J/ψπ^+π^-π^0$ decays

With the newly measurements of $X(3872) \to J/ψπ^+π^-$ from LHCb Collaboration, in addition to the dominant contribution from the $ρ^0$ meson, we perform a theoretical study on the contribution of $ω$ meson in the $X(3872) \to J/ψπ^+π^-$ and $X(3872)\to J/ψπ^+π^-π^0$ processes. It is found that the recent experimental measurements on the $π^+ π^-$ invariant mass distributions can be well reproduced, and the ratio of the couplings between $X(3872) \to J/ψρ^0$ and $X(3872) \to J/ψω$ is also evaluated. Within the parameters extracted from the $π^+ π^-$ invariant mass distributions of the $X(3872) \to J/ψπ^+π^-$ process, the branching fractions of the $X(3872) \to J/ψω$ channel relative to that of the $X(3872) \to J/ψπ^+π^-π^0$ channel and the $π^+ π^- π^0$ invariant mass distributions of the $X(3872) \to J/ψπ^+π^-π^0$ decay are calculated, which gives a hint for the further high-statistic experiment.

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arXiv2022

Theoretical study of the process $D^+_s \to π^+ K^0_S K^0_S$ and the isovector partner of $f_0(1710)$

We present a theoretical study of $a_0(1710)$, the isovector partner of $f_0(1710)$, in the process $D^+_s \to π^+ K^0_SK^0_S$. The weak interaction part proceeds through the charm quark decay process: $c(\bar{s}) \to (s + \bar{d} + u)(\bar{s})$, while the hadronization part takes place in two mechanisms, differing in how the quarks from the weak decay combines into $πK^*$ with a quark-antiquark pair $q\bar{q}$ with the vacuum quantum numbers. In addition to the contribution from the tree diagram of the $K^{*+} \to π^+ K^0_S$, we have also considered the $K^*\bar{K}^*$ final-state interactions within the chiral unitary approach to generate the intermediate state $a_0(1710)$, then it decays into the final states $K^0_SK^0_S$. We find that the recent experimental measurements on the $K^0_SK^0_S$ and $π^+K^0_S$ invariant mass distributions can be well reproduced, and the proposed mechanism can provide valuable information on the nature of scalar $f_0(1710)$ and its isovector partner $a_0(1710)$.

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arXiv2022

Roles of $a_0(980)$, $Λ(1670)$, and $Σ(1385)$ in the $Λ_c^+ \to ηΛπ^+$ decay

Recently, the Belle Collaboration has measured the $Λ_c^+ \to ηΛπ^+$ decay and reported the $ηΛ$ and $Λπ^+ $ invariant mass distributions, which show the clear signals of the resonances $Λ(1670)$ and $Σ(1385)$, respectively. Based on our previous works [Eur. Phys. J. C 76 (2016) 496 and Phys. Rev. D 95 (2017) 074024], we re-analyze this process by considering the $S$-wave $ηΛ$ and $ηπ^+$ final state interactions within the chiral unitary approach, which dynamically generate the $Λ(1670)$ and $a_0(980)$, respectively. Our results are in good agreement with the Belle measurements, which supports the molecular nature of the $Λ(1670)$ and $a_0(980)$. In addition, the $ηπ^+$ invariant mass distributions are also computed and a cusp structure of $a_0(980)$ is cleary shown around the $K\bar{K}$ mass threshold.

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arXiv2022

Faddeev fixed-center approximation to the $D\bar{D}K$ system and the hidden charm $K_{c\bar{c}}(4180)$ state

We perform a theoretical study on the $D\bar{D}K$ three body system, using the fixed center approximation to the Faddeev equations, considering the interaction between $D$ and $K$, $D$ and $\bar{D}$ from the chiral unitary approach. We assume the scattering of $K$ meson on a clusterized system $D\bar{D}$, where a scalar meson $X(3720)$ could be formed. Thanks to the strong $DK$ interaction, where the scalar $D^*_{s0}(2317)$ meson is dynamically generated, a resonance structure shows up in the modulus squared of the three body $K$-$(D\bar{D})_{X(3720)}$ scattering amplitude and supports that a $D\bar{D}K$ bound state can be formed. The result is in agreement with previous theoretical studies, which claim a new excited hidden charm $K$ meson, $K_{c\bar{c}}(4180)$ with quantum numbers $I(J^P) = \frac{1}{2}(0^-)$ and mass about $4180$ MeV. It is expected that these theoretical results motivate its search in experimental measurements.

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arXiv2022

Investigations on the flavor-dependent axial charges of the octet baryons

We have investigated the axial charges of the ground octet baryons within the extended chiral constituent quark model, where all the possible compact five-quark Fock components $qqq(q\bar{q}) (q=u, d, s)$ in the baryons are considered. The transition couplings between the three- and five-quark components in the baryons are assumed to be via the $^{3}P_{0}$ mechanism, which could reproduce the sea asymmetry in proton very well. The numerical results for the flavor-dependent axial charges of the octet baryons are comparable to those predicted by other theoretical approaches. It is shown that the singlet axial charges of the octet baryons, which should indicate total baryons spin arising from the spin of the quarks, fall in the range $0.45-0.75$ in present model. This is in consistent with the predictions by lattice QCD and chiral perturbation theory. It's also very interesting that the light quarks spin $Δu$ and $Δd$ in the $Λ$ baryon are of small but negative values, which exactly vanish in the traditional three-quark model.

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arXiv2022

Hadron spectroscopy at STCF

Despite that quantum chromodynamics, the theory of strong interaction, has colorful quarks and gluons as its basic degrees of freedom, all fundamental particles participating the strong interaction that can be directly detected in experiments are colorless or color-singlet hadrons. This phenomenon is called color confinement. Because of that, the study of hadron spectroscopy is essential in improving our understanding of the nonperturbative regime of QCD and to reveal the mechanism of color confinement. The high-luminosity electron-positron collision machine under discussion, Super tau-Charm Facility (STCF), can play an essential role in hadron spectroscopy by discovering new hadron resonances and measuring properties of known hadrons with an unprecedented precision. In the following, we will discuss briefly the topics on hadron spectroscopy that will be investigated at STCF.

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arXiv2022

Electromagnetic form factors of $Λ$ hyperon in the vector meson dominance model and a possible explanation of the near-threshold enhancement of the $e^+e^- \to Λ\barΛ$ reaction

The near-threshold $e^+e^- \to Λ\barΛ$ reaction is studied with the assumption that the production mechanism is due to a near-$Λ\barΛ$-threshold bound state. The cross section of $e^+e^- \to Λ\barΛ$ reaction is parametrized in terms of the electromagnetic form factors of $Λ$ hyperon, which are obtained with the vector meson dominance model. It is shown that the contribution to the $e^+e^- \to Λ\barΛ$ reaction from a new narrow state with quantum numbers $J^{PC}=1^{--}$ is dominant for energies very close to threshold. The mass of this new state is around 2231 MeV, which is very close to the mass threshold of $Λ\barΛ$, while its width is just a few MeV. This gives a possible solution to the problem that all previous calculations seriously underestimate the near-threshold total cross section of the $e^+e^- \to Λ\barΛ$ reaction. We also note that the near-threshold enhancement can be also reproduced by including these well established vector resonances $ω(1420)$, $ω(1650)$, $ϕ(1680)$, or $ϕ(2170)$ with a Flatt${\rm\acute{e}}$ form for their total decay width, and a strong coupling to the $Λ\barΛ$ channel.

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