Xue-Qian Li

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

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Publications (203)509.28 Total impact

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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.
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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.
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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.
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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 .
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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 $Z_c(4025)$($Z_c(4020)$).
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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.
    European Physical Journal C 09/2014; 74(12). DOI:10.1140/epjc/s10052-014-3198-3 · 5.44 Impact Factor
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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.
    Physical Review D 08/2014; 90(5). DOI:10.1103/PhysRevD.90.053009 · 4.86 Impact Factor
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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.
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    ABSTRACT: The supersymmetry (SUSY) may be the most favorable extension of the standard model, 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 at future ILC which may provide sufficient energy to produce SUSY particles if they are not too heavy as suggested by many authors and low background environment. The superflavor symmetry associates baryons with mesons as long as both of them contain a heavy constituent and a light one. Thus in this work, we are able to calculate the production rate of SUSY baryons near their production threshold in terms of the $B\bar B$ production data. Our analysis unambiguously indicates that the future ILC data would determine if the SUSY particles with a mass below $\sqrt s/2$ ($\sqrt s$ is the ILC energy) indeed exist.
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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.
    Physical Review D 12/2013; 89(1). DOI:10.1103/PhysRevD.89.017501 · 4.86 Impact Factor
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    ABSTRACT: In contrast with $B^0-\bar B^0$, $B_s-\bar B_s$ mixing where the standard model (SM) contributions overwhelm that of new physics beyond standard model (BSM), a measured relatively large $D^0-\bar D^0$ mixing where the SM contribution is negligible, definitely implies the existence of new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the rare decay $D^0\to \mu^+\mu^-$ could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of new physics BSM in the leptonic decays of $D^0$, concretely we discuss the contributions of unparticle or an extra gauge boson $Z'$ while imposing the constraints set by fitting the $D^0-\bar D^0$ mixing data. We find that the long-distance SM effects for $D^0\to l\bar l$ still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as $D^0\to \mu^{\pm}e^{\mp}$, the new physics contribution would be significant.
  • Hong-Wei Ke, Zheng-Tao Wei, Xue-Qian Li
    European Physical Journal C 10/2013; 73(10). DOI:10.1140/epjc/s10052-013-2561-0 · 5.44 Impact Factor
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    Lian-Bao Jia, Xue-Qian Li
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    ABSTRACT: The new observation of CDMS II favors low mass WIMPs. Taking the CDMS II new results as input and following the literature we consider a SM singlet: the darkon as the dark matter candidate, which can be either scalar, fermion or vector. It is found that the simplest scenario of DM+SM conflicts with the stringent constraint set by the LHC data. New physics beyond the SM is needed as many authors suggested. In this work, we discuss an extended standard model $SU_L(2)\otimes U_Y(1)\otimes U(1)'$ where $U(1)'$ only couples to the darkon. The new gauge symmetry is broken into $U_{em}(1)$ and two neutral bosons $Z^0$ and $Z'$ which are mixtures of $W^3_{\mu},\; B_{\mu}\; X_{\mu}$ are resulted in, where $Z^0$ is very close to the $Z$ boson of the standard model. Following the literature and based on the CDMS data, we make a complete analysis to testify the validity of the model. The cross section of the elastic scattering between darkon and nucleon is calculated, and the DM relic density is evaluated in the extended scenario as well. It is found that considering the constraints from both cosmology and collider experiments, only if $Z'$ is lighter than $Z^0$, one can reconcile all the presently available data.
    Physical Review D 09/2013; 89(3). DOI:10.1103/PhysRevD.89.035006 · 4.86 Impact Factor
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    ABSTRACT: We calculate the forward backward asymmetry of the top-pair production at TEVATRON up to next to leading order (NLO) in the little Higgs model (LHM). We find that the contribution of $Z_H$ can be large enough to make up the gap between standard model (SM) prediction and data. With the database of $7.65\pm0.20\pm0.36$ pb, therefore, the parameter space for flavor-changing coupling of $Z_H$ is constrained. Thus this model can result in the required asymmetry while the total cross section of top-pair production remaining consistent with data.
    Chinese Physics C 09/2013; 38(11). DOI:10.1088/1674-1137/38/11/113102 · 0.82 Impact Factor
  • Hong-Wei Ke, Ya-Zheng Chen, Xue-Qian Li
    Chinese Physics Letters 09/2013; 30(9):099901. DOI:10.1088/0256-307X/30/9/099901 · 0.95 Impact Factor
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    Hong-Wei Ke, Zheng-Tao Wei, Xue-Qian Li
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    ABSTRACT: Assuming the newly observed $Z_c(3900)$ to be a molecular state of $D\bar D^*(D^{*} \bar D)$, we calculate the partial widths of $Z_c(3900)\to J/\psi+\pi;\; \psi'+\pi;\; \eta_c+\rho$ and $D\bar D^*$ within the light front model (LFM). $Z_c(3900)\to J/\psi+\pi$ is the channel by which $Z_c(3900)$ was observed, our calculation indicates that it is indeed one of the dominant modes whose width can be in the range of a few MeV depending on the model parameters. Similar to $Z_b$ and $Z_b'$, Voloshin suggested that there should be a resonance $Z_c'$ at 4030 MeV which can be a molecular state of $D^*\bar D^*$. Then we go on calculating its decay rates to all the aforementioned final states and as well the $D^*\bar D^*$. It is found that if $Z_c(3900)$ is a molecular state of ${1\over\sqrt 2}(D\bar D^*+D^*\bar D)$, the partial width of $Z_c(3900)\to D\bar D^*$ is rather small, but the rate of $Z_c(3900)\to\psi(2s)\pi$ is even larger than $Z_c(3900)\to J/\psi\pi$. The implications are discussed and it is indicated that with the luminosity of BES and BELLE, the experiments may finally determine if $Z_c(3900)$ is a molecular state or a tetraquark.
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    ABSTRACT: Considering the CP violating phases, we analyze the neutron electric dipole moment (EDM) in a CP violating supersymmetric extension of the standard model where baryon and lepton numbers are local gauge symmetries(BLMSSM). The contributions from the one loop diagrams and the Weinberg operators are taken into account. Adopting some assumptions on the relevant parameter space, we give the numerical results analysis. The numerical results for neutron EDM can reach $1.05\times 10^{-25}(e.cm)$, which is about the experimental upper limit.
    Journal of High Energy Physics 06/2013; 10(2013):020. DOI:10.1007/JHEP10(2013)020 · 6.22 Impact Factor
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    ABSTRACT: The CDEX Collaboration has been established for direct detection of light dark matter particles, using ultra-low energy threshold p-type point-contact germanium detectors, in China JinPing underground Laboratory (CJPL). The first 1 kg point-contact germanium detector with a sub-keV energy threshold has been tested in a passive shielding system located in CJPL. The outputs from both the point-contact p+ electrode and the outside n+ electrode make it possible to scan the lower energy range of less than 1 keV and at the same time to detect the higher energy range up to 3 MeV. The outputs from both p+ and n+ electrode may also provide a more powerful method for signal discrimination for dark matter experiment. Some key parameters, including energy resolution, dead time, decay times of internal X-rays, and system stability, have been tested and measured. The results show that the 1 kg point-contact germanium detector, together with its shielding system and electronics, can run smoothly with good performances. This detector system will be deployed for dark matter search experiments.
    Chinese Physics C 05/2013; 37(12). DOI:10.1088/1674-1137/37/12/126002 · 0.82 Impact Factor

Publication Stats

1k Citations
509.28 Total Impact Points

Institutions

  • 1994–2015
    • Nankai University
      • Department of Physics
      T’ien-ching-shih, Tianjin Shi, China
  • 2004–2011
    • Chinese Academy of Sciences
      • • Department of Physics
      • • Institute of Theoretical Physics
      Peping, Beijing, China
  • 2010
    • Guangxi Normal University
      Ling-ch’uan, Guangxi Zhuangzu Zizhiqu, China
  • 2007
    • Peking University
      • Department of Physics
      Peping, Beijing, China
  • 2005
    • National Taiwan University
      • Department of Physics
      T’ai-pei, Taipei, Taiwan
  • 2002
    • University of Adelaide
      • Special Research Centre for the Subatomic Structure of Matter
      Tarndarnya, South Australia, Australia
  • 1990–1997
    • Academia Sinica
      T’ai-pei, Taipei, Taiwan