Xue-Qian Li

Nankai University, T’ien-ching-shih, Tianjin Shi, China

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Publications (219)546.52 Total impact

  • Hong-Wei Ke · Xue-Qian Li
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    ABSTRACT: At the invariant mass spectrum of $h_c\pi^\pm$ a new resonance $Z_c(4020)$ has been observed, however the previously confirmed $Z_c(3900)$ does not show up at this channel. In this paper we assume that $Z_c(3900)$ and $Z_c(4020)$ are molecular states of $D\bar D^*(D^{*} \bar D)$ and $D^*\bar D^*$ respectively, then we calculate the transition rates of $Z_c(3900)\to h_c+\pi$ and $Z_c(4020)\to h_c+\pi$ in the light front model. Our results show that the partial width of $Z_c(3900)\to h_c+\pi$ is only three times smaller than that of $Z_c(4020)\to h_c+\pi$. $Z_c(4020)$ seems to be a molecular state, so if $Z_c(3900)$ is also a molecular state it should be observed in the portal $e^+e^-\to h_c\pi^\pm$ as long as the database is sufficiently large, by contrary if the future more precise measurements still cannot find $Z_c(3900)$ at $h_c\pi^\pm$ channel, the molecular assignment to $Z_c(3900)$ should be ruled out.
    No preview · Article · Jan 2016
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    Xuewen Liu · Hong-Wei Ke · Xiang Liu · Xue-Qian Li
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    ABSTRACT: The structures of the $X,Y,Z$ exotic states which recently are experimentally observed one after another, have composed a challenge to our understanding of the fundamental principles in the hadron physics and the relevant study will definitely shed light on the concerned physics. Generally the four-quark states might be in a molecular state or teraquark or their mixture. In this work, we adopt the suggestion that $Y(4630)$ is a charmonium-like tetraquark made of a diquark and an anti-diquark. If it is true, its favorable decay mode should be $Y(4360)$ decaying into an open-charm baryon pair, since such a transition occurs via strong interaction and is super-OZI-allowed. In this work, we calculate the decay width of $Y(4630)\to\Lambda^+_c\Lambda^-_c$ in the framework of the quark pair creation (QPC) model. The numerical results suggest that the $Y(4630)$ state is a radially excited state.
    Preview · Article · Jan 2016
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    Tai-Fu Feng · Xue-Qian Li · Hai-Bin Zhang · Shu-Min Zhao
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    ABSTRACT: In a supersymmetric extension of the standard model where baryon and lepton numbers are local gauge symmetries, we analyze the signals of decay channels $\Phi\rightarrow gg$, $\Phi\rightarrow\gamma\gamma$ and $\Phi\rightarrow \bar{t}t,\;VV\;(V=Z,\;W)$ with the CP-odd scalar $\Phi=A_{_B}^0$ mass around $750\;{\rm GeV}$ which is observed at the LHC at a center of mass energy of $13\;{\rm TeV}$. Adopting some assumptions on relevant parameter space, the CP-odd scalar $A_{_B}^0$ can account for the experimental data on $750\;{\rm GeV}$ diphoton excess from ATLAS and CMS naturally.
    Preview · Article · Dec 2015
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    Dian-Yong Chen · Xiang Liu · Xue-Qian Li · Hong-Wei Ke
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    ABSTRACT: We propose that the unified Fano-like interference picture applies to $e^+e^-\to \pi^+\pi^- J/\psi$ and $e^+e^-\to \pi^+\pi^- \psi(3686)$, where $Y(4260)$ and $Y(4360)$ are observed, respectively, to provide a reasonable interpretation of the asymmetric lineshapes of $Y(4260)$ and $Y(4360)$ structures. Moreover, the Fano-like interference induces an extra broad structure $Y(4008)$ in $e^+e^-\to \pi^+\pi^- J/\psi$ as a companion peak to $Y(4260)$. Three charmonium-like states $Y(4008)$, $Y(4260)$ and $Y(4360)$ observed in $e^+e^-$ annihilation processes are not genuine resonances. Under this scenario, it is well explained why $Y(4008)$, $Y(4260)$ and $Y(4360)$ are absent in the experimental data of the $R$ value scan and missing in open-charm decay channels. Although the present work presents the a typical application of the Fano-like interference in the particle physics at the lower energy region, we have reason to believe that the Fano-like phenomena may exist in other processes such as $e^+e^-\to \pi^+\pi^-\psi(3770)$ and $e^+e^-\to K^+K^- J/\psi$, which will be accessible at BESIII and forthcoming BelleII.
    Preview · Article · Dec 2015
  • Xing-Dao Guo · Si-Run Xue · Hong-Wei Ke · Xue-Qian Li · Qiang Zhao
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    ABSTRACT: We study the decay process of $J/\psi\rightarrow e^+e^- \phi$ where the relatively clean electromagnetic (EM) transitions appear at leading order at tree level while the hadronic contributions only emerge via hadronic loop transitions. We include the low-lying scalar $f_0(980)$ and pseudoscalar $\eta/\eta'$ as the dominant contributions in the evaluation of the hadronic loop contributions. It is found that the hadronic effects are negligible comparing with the EM contributions. The decay width of $J/\psi\rightarrow e^+e^- \phi$ is determined to be about $2.12\times 10^{-6}$ keV if there is no any other leading mechanism contributing, and this result will be tested by the BESIII experiment with a large data sample of $J/\psi$.
    No preview · Article · Dec 2015
  • Xing-Dao Guo · Xuewen Liu · Hong-Wei Ke · Xue-Qian Li
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    ABSTRACT: The QCD multipole expansion (QCDME) is based on the quantum field theory, so should be more reliable. However, on another aspect, it refers to the non-perturbative QCD , so that has a certain application range. Even though it successfully explains the data of transition among members of the $\Upsilon$ ($\psi$) family, as Eichten indicates, beyond the production threshold of mediate states it fails to meet data by several orders. In this work, by studying a simple decay mode $D^*\to D+\pi^0$, where a pion may be emitted before $D^*$ transiting into $D$, we analyze the contribution of QCD multipole expansion. Whereas as the $D\pi$ portal is open, the dominant contribution is an OZI allowed process where a light quark-pair is excited out from vacuum and its contribution can be evaluated by the $^3P_0$ model. Since the direct pion emission is a process which is OZI suppressed and violates the isospin conservation, its contribution must be much smaller than the dominant one. By a careful calculation, we may quantitatively estimate how small the QCDME contribution should be and offer a quantitative interpretation for Eichten's statement.
    No preview · Article · Nov 2015
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    Xuewen Liu · Ligong Bian · Xue-Qian Li · Jing Shu
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    ABSTRACT: In this work, we introduce an extra pseudoscalar into the Type-III two-Higgs doublet model (2HDM). In the framework of the extended 2HDM, the $h\rightarrow\mu\tau$ excess measured at CMS and $(g-2)_{\mu}$ anomaly can be simultaneously explained within a parameter space which is not ruled out by the flavor-violating process $\tau\rightarrow\mu\gamma$. Moreover, existence of the pseudo-scalar provides an opportunity to interpret the Galactic Center gamma ray excess(GCE) which might be caused by dark matter(DM) pair annihilations. It is also noted that to meet the observed DM relic density, other DM annihilation channels are needed.
    Full-text · Article · Aug 2015
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    Rui Chen · Xiang Liu · Xue-Qian Li · Shi-Lin Zhu
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    ABSTRACT: The discovery of the new resonances $P_c(4380)$ and $P_c(4450)$ indeed opens a new page for hadron physics. They are identified as the long-expected pentaquarks. Now the Gell-Mann's quark model is complete. On the other aspect, the light multiquark exotic states are not stable, so cannot exist individually but mix with the regular structures with the same quantum numbers. With heavy flavors which play an important role to stabilize the systems, the multiquark states are able to exist. The allegation is not only true for the exotic mesons which have already been experimentally observed and named as $X$, $Y$, $Z$ particles, but also for the baryons which have $Q\bar Q qqq$ structures. Further experimental and theoretical research should be pursued in the future.
    Full-text · Article · Jul 2015 · Physical Review Letters
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    Hong-Wei Ke · Song-Xue Zhao · Xue-Qian Li
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    ABSTRACT: Investigating the CKM matrix in different parametrization schemes, it is noticed that those schemes can be divided into a few groups where the sine values of the CP phase for each group are approximately equal. Using those relations, several approximate equalities among the elements of CKM matrix are established. Assuming them to be exact, there are infinite numbers of solutions and by choosing special values for the free parameters in those solutions, several textures presented in literature are obtained. The case can also be generalized to the PMNS matrix for the lepton sector. In parallel, several mixing textures are also derived by using presumed symmetries, amazingly, some of their forms are the same as what we obtained, but not all. It hints existence of a hidden symmetry which is broken in the practical world. The nature makes its own selection on the underlying symmetry and the way to break it, while we just guess what it is.
    Preview · Article · Jun 2015
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    Full-text · Dataset · May 2015
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    Full-text · Dataset · Mar 2015
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    Hong-Wei Ke · Jia-Hui Zhou · Shuai Chen · Tan Liu · Xue-Qian Li
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    ABSTRACT: The approximately symmetric form of the PMNS matrix suggests that there could exist a hidden symmetry which makes the PMNS matrix different from the CKM matrix for quarks. In literature, all the proposed fully symmetric textures exhibit an explicit $\mu-\tau$ symmetry in addition to other symmetries which may be different for various textures. Observing obvious deviations of the practical PMNS matrix elements from those in the symmetric textures, there must be a mechanism to distort the symmetry. It might be due to existence of light sterile neutrinos. In this work, we study the case of the Tribimaximal texture and propose that its apparent symmetry disappears due to existence of a sterile neutrino. We observe that introducing just one sterile neutrino is still not sufficient to recover the data, thus a slight $\mu-\tau$ symmetry breaking is also needed. By considering those factors, we obtain the PMNS matrix elements which are consistent with data within the experimental tolerance.
    Preview · Article · Feb 2015 · Modern Physics Letters A
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    Hong-Wei Ke · Xue-Qian Li
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    ABSTRACT: Observing the CKM matrix elements written in different parametrization schemes, one can notice obvious relations among the sine-values of the CP phases in those schemes. Using the relations, we establish a few parametrization-independent equations, by which the matrix elements of the CKM matrix can be completely fixed up to a universal parameter. If it is true, we expect that there should exist a hidden symmetry in the nature which determines the relations. Moreover, it requires a universal parameter, naturally it would be the famous Jarlskog invariant which is also parametrization independent. Thus the four parameters (three mixing angles and one CP phase) of the CKM matrix are not free, but determined by the symmetry and the universal parameter. As we generalize the rules to the PMNS matrix for neutrino mixing, the CP phase of the lepton sector is predicted to be within a range of $0\sim 59^\circ$ centered at $39^\circ$ (in the P$_a$ parametrization) which will be tested in the future experiments.
    Preview · Article · Nov 2014 · Communications in Theoretical Physics
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    Hong-Wei Ke · Jia-Hui Zhou · Xue-Qian Li
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    ABSTRACT: The observed resonance peak around 2.86 GeV has been carefully reexamined by the LHCb collaboration and it is found that under the peak there reside two states $D^*_{s1}(2860)$ and $D^*_{s3}(2860)$ which are considered as $1^3D_1(c\bar s)$ and $1^3D_3(c\bar s)$ with slightly different masses and total widths. Thus, the earlier assumption that the resonance $D^*_{s1}(2710)$ was a $1D$ state should not be right. We suggest to measure the partial widths of radiative decays of $D^*_{sJ}(2860)$ and $D^*_{s1}(2710)$ to confirm their quantum numbers. We would consider $D^*_{s1}(2710)$ as $2^3S_1$ or a pure $1^3D_1$ state, or their mixture and respectively calculate the corresponding branching ratios as well as those of $D^*_{sJ}(2860)$. The future precise measurement would provide us information to help identifying the structures of those resonances .
    Preview · Article · Nov 2014 · European Physical Journal C
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    Xue-Wen Liu · Hong-Wei Ke · Yi-Bing Ding · Xue-Qian Li
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    ABSTRACT: In this work, we use the Born-Oppenheimer approximation where the potential between atoms can be approximated as a function of distance between the two nuclei to study the four-quark bound states. By the approximation, Heitler and London calculated the spectrum of hydrogen molecule which includes two protons (heavy) and two electrons (light). Generally, the observed exotic mesons $Z_b(10610)$, $Z_b(10650)$, $Z_c(3900)$ and $Z_c(4025)$($Z_c(4020)$) may be molecular states of two physical mesons and/or in diquark-anti-diquark structures. In analog to the Heitler-London method for calculating the mass of hydrogen molecule, we investigate whether there exist energy minima for these two structures. By contrary to the hydrogen molecule case where only the spin-triplet possesses an energy minimum, there exist minima for both of them. It implies that both molecule and tetraquark states can be stable objects. But since they have the same quantum numbers, the two states may mix to result in physical states. A consequence would be that one may expect to experimentally observe partner exotic states co-existing with $Z_b(10610)$, $Z_b(10650)$, $Z_c(3900)$ and $Z_c(4025)$($Z_c(4020)$).
    Preview · Article · Sep 2014 · Chinese Physics C
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    Xue-Qian Li · Xiang Liu
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    ABSTRACT: Based on the fact that the long expected pentaquark which possesses exotic quantum numbers of $B=1$ and $S=1$ was not experimentally found, but exotic states of $XYZ$ have been observed recently, we conjecture that the heavy flavors may play an important role for stabilizing the hadronic structures beyond the traditional $q\bar q$ and $qqq$ composites.
    Preview · Article · Sep 2014 · European Physical Journal C
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    Hong-Wei Ke · Tan Liu · Xue-Qian Li
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    ABSTRACT: It is suggested that there is an underlying symmetry which relates the quark and lepton sectors. Namely, among the mixing matrix elements of CKM for quarks and PMNS for leptons there exist complementarity relations at a high energy scale (such as the see-saw or even the GUT scales). Assuming that the relations would remain during the matrix elements running down to the EW scale. Observable breaking of the rational relation is attributed to existence of sterile neutrinos which mix with the active neutrino to result in the observable PMNS matrix. We show that involvement of a sterile in the (3+1) model, induces that $|U_{e4}|^2= 0.040$, $|U_{\mu4}|^2= 0.009$ and $\sin^2 2\alpha=0.067$. We also find a new self-complementarity $\vartheta_{12}+\vartheta_{23}+\vartheta_{13}+\alpha\approx90^\circ$. The numbers are generally consistent with those obtained by fitting recent measurements, especially in this scenario, the existence of a sterile neutrino does not upset the LEP data i.e. the number of neutrino types is very close to 3.
    Preview · Article · Aug 2014 · Physical Review D
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    ABSTRACT: The China Dark Matter Experiment (CDEX) is located at the China Jinping underground laboratory (CJPL) and aims to directly detect the WIMP flux with high sensitivity in the low mass region. Here we present a study of the predicted photon and electron backgrounds including the background contribution of the structure materials of the germanium detector, the passive shielding materials, and the intrinsic radioactivity of the liquid argon that serves as an anti-Compton active shielding detector. A detailed geometry is modeled and the background contribution has been simulated based on the measured radioactivities of all possible components within the GEANT4 program. Then the photon and electron background level in the energy region of interest (<10^-2 events kg-1 day-1 keV-1 (cpkkd)) is predicted based on Monte Carlo simulations. The simulated result is consistent with the design goal of CDEX-10 experiment, 0.1 cpkkd, which shows that the active and passive shield design of CDEX-10 is effective and feasible.
    Full-text · Article · Feb 2014 · Chinese Physics C
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    Lian-Bao Jia · Xing-Dao Guo · Hong-Ying Jin · Xue-Qian Li
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    ABSTRACT: The supersymmetry (SUSY) may be one of the most favorable extensions of the standard model (SM), however, so far at LHC no evidence of the SUSY particles were observed. An obvious question is whether they have already emerged, but escaped from our detection, or do not exist at all. We propose that the future ILC may provide sufficient energy to produce SUSY particles if they are not too heavy in the low background environment. The superflavor symmetry associates baryons with mesons as long as both of them containing a heavy constituent and a light one. In this work, we estimate the production rate of SUSY baryons near their production threshold in terms of the $B\bar B$ production data. Our analysis indicates that if the SUSY baryons with masses below $\sqrt s/2$ ($\sqrt s$ is the ILC energy) exist, they could be observed at future ILC.
    Preview · Article · Jan 2014 · Chinese Physics C
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    Hong-Wei Ke · Tan Liu · Xue-Qian Li
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    ABSTRACT: The LHCb Collaboration has systematically measured the rates of Bc→J /ψK, Bc→J/ψDs, Bc→J /ψDs*, and Bc→ψ(2S)π. The new data enable us to study relevant theoretical models and further determine the model parameters. In this work, we calculate the form factors for the transitions Bc→J /ψ and Bc→ψ(2S) numerically and then determine the partial widths of the semileptonic and nonleptonic decays. The theoretical predictions on the ratios of Γ(Bc→J/ψK)/Γ(Bc→J/ψπ), Γ(Bc→J/ψDs)/Γ(Bc→J/ψπ), and Γ(Bc→J/ψDs*)/Γ(Bc→J/ψπ) are consistent with data within only 1σ. Especially, for calculating Γ(Bc→ψ(2S)X) the modified harmonic oscillator wave function which we developed in early works is employed, and the results indicate that the modified harmonic oscillator wave function works well.
    Preview · Article · Dec 2013 · Physical Review D

Publication Stats

2k Citations
546.52 Total Impact Points

Institutions

  • 1993-2015
    • Nankai University
      • Department of Physics
      T’ien-ching-shih, Tianjin Shi, China
  • 2007
    • Peking University
      • Department of Physics
      Peping, Beijing, China
  • 2005
    • National Taiwan University
      • Department of Physics
      T’ai-pei, Taipei, Taiwan
  • 2004
    • Chinese Academy of Sciences
      • Institute of Theoretical Physics
      Peping, Beijing, China
  • 1990-1997
    • Academia Sinica
      T’ai-pei, Taipei, Taiwan