Study on Production of Exotic 0 Meson D*sJ(2317) in Decays of ψ(4415)

The newly observed D*sJ family containing D*sJ(2317), DsJ(2460), and DsJ(2632) attracts great interests.Determining their structures may be an important task for both theorists and experimentalists. In this work we use a non-relativistic model (the harmonic oscillator model) to evaluate the production rate of D*sJ (2317) from the decays of ψ(4415). For a comparison, we also employ the widely adopted heavy quark effective theory to repeat the calculation.We find that the rate is sizable and may be observed at BES Ⅲ and CLEO, if it is a p-wave excited state of Ds (1968).Unfortunately, the other two members of the family cannot be observed through decays of charmonia, because of the constraints from the final state phase space.     

Chiral SU（3） Quark Model Study of Tetraquark States： cnn^-s^-/css^-s^-

The new members of the charm-strange family Dsj^＊（2317）, Dsj（2460）, and Ds（2632）, which have the surprising properties, are challenging the present models. Many theoretical interpretations have been devoted to this issue. Most authors suggest that they are not the conventional cs^- quark model states, but possibly are four-quark states, molecule states, or mixtures of a P-wave cs^- and a four-quark state. In this work, we follow the four-quark-state picture, and study the masses of cnn^-s^-/css^-s^- states （n is u or d quark） in the chiral SU（3） quark model. The numerical results show that the mass of the mixed four-quark state （cnn^-s^-/css^-s^-） with spin parity j^P ： 0^＋ might not be Ds （2632）. At the same time, we also conclude that Dsj^＊（2317） and Dsj（2460） cannot be explained as the pure four-quark state.     

S-Wave DK Interactions in the Chiral SU（3） Quark Model

The DK interaction is relevant to the interpretation of the DsJ（2317）. We dynamically investigate S-wave DK interactions in the chiral SU（3） quark model by solving the resonating group method equation. The numerical results show an attraction between D and K, which is from boson exchanges between light quarks. However, such an attraction is not strong enough to form a DK molecule. Meanwhile, S partial wave phase shifts of DK elastic scattering are obtained. The case of S-wave D^＊K is rather similar to that of DK. To draw a definite conclusion of whether a molecular state exists in DK or the D^＊K system, more details of dynamics should be considered in a future study.     

Dynamical study of the possible molecular state X（3872） with the s-channel one gluon exchange interaction

The recently observed X（3872） resonance, which is difficult to assign a conventional cc charmonium state in the quark model, may be interpreted as a molecular state. Such a molecular state is a hidden flavor four quark state because of its charmonium-like quantum numbers. The s-channel one gluon exchange is an interaction which only acts in the hidden flavor multi-quark system. In this paper, we will study the X（3872） and other similiar hidden flavor molecular states in a quark model by taking into account the s-channel one gluon exchange interaction.     

QQqq Four-Quark Bound States in Chiral SU（3） Quark Model

Abstract The possibility of QQqq heavy-light four-quark bound states has been analyzed by means of the chiral SU（3） quark model, where Q is the heavy quark （c or b） and q is the light quark （u, d, or s）. We obtain a bound state for the bbnn configuration with quantum number JR=1^＋, I = 0 and for the ccnn （JR=1^＋, I=O） configuration, which is not bound but slightly above the D^＊ D^＊ threshold （n is u or d quark）. Meanwhile, we also conclude that a weakly bound state in bbnn system can also be found without considering the ehiral quark interactions between the two light quarks, yet its binding energy is weaker than that with the chiral quark interactions.     

Lepton Flavor Violating Z →lIlJ in SO（3） Gauge Extension of SM

The SO（3） gauge extension of SM, which is proposed to present a successful explanation for the observed small masses of neutrino and the nearly tri-bimaximal neutrino mixing, predicted the vector-like SO（3） triplet Majorana neutrinos and SUL（2） double Higgs bosons. In this work we calculate branching ratios of the charged lepton flavor violating decays lIlJV （V = γ, Z） induced by these Majorana neutrinos and Higgs bosons. We find that under the model parameters constrained by experimental bounds on the decays Z →lIlJ, the branching ratio of decays lI→lJγ can be up to 10^-10, which may be accessible at the future experiments.     

Hadron molecules

We discuss a possible interpretation of the open charm mesons D＊s0 （2317）,D s1 （2460） and the hidden charm mesons X（3872）,Y（3940） and Y（4140） as hadron molecules.Using a phenomenological Lagrangian approach we review the strong and radiative decays of the D＊ s0 （2317） and D s1 （2460） states.The X（3872） is assumed to consist dominantly of molecular hadronic components with an additional small admixture of a charmonium configuration.Determing the radiative （γJ/ψ and γψ（2s）） and strong （J/ψ2π and J/ψ3π） decay modes we show that the present experimental observation is consistent with the molecular structure assumption of the X（3872）.Finally,we give evidence for molecular interpretations of the Y（3940） and Y（4140） related to the observed strong decay modes J/ψ＋ω or J/ψ＋φ,respectively.     

Five-quark components in N＊（1535）

Here we employ the extended chiral constituent quark model to investigate the five-quark components in the N＊ （1535） resonance. The axial charge of N＊（1535） and the electromagnetic transition γ＊N → N＊（1535） are also analyzed. The results show that there may be sizable strangeness component in N＊（1535）.     

B→0^＋（1^＋）＋ missing energy in unparticle physics

We examine the effects of an unparticle U as a possible source of missing energy in the p-wave decays of a B meson. The dependence of the differential branching ratio on the K0^＊ （K1） - meson＇s energy is discussed in the presence of scalar and vector unparticle operators and significant deviation from the standard model value is found after addition of these operators. Finally, we have shown the dependence of the branching ratio for the above-mentioned decays on the parameters of unparticle stuff like effective couplings, cutoff scale Au and the scale dimensions du.     

Study of Radiative Decays Ds1（2536） → Ds（1968） ＋γ and Ds1（2536）→ Ds^＊（2112） ＋ γ in CQM Model

There are some uncertain charazteristics of the Ds1（2536）, which deserves further discussion. Based on the assumption that the meson is constituted by c s, and belongs to T doublet （1^＋, 2^＋）, radiative decays Ds1（2536） → Ds（1968） ＋γ and Ds1（2536） → Ds^＊（2112） ＋ γ are studied in the CQM model The large branching ratios of them from our calculations not only indicate the process may be detected in the future experiments, but also can give a deep comprehension of the structure of it.     

QCD Sum Rules Study of X（4350）

The QCD sum rule approach is used to analyze the nature of the recently observed new resonance X （4350）, which is assumed to be a diquark-antidiquark state [cs][cs] with jPC = 1-＋. The interpolating current representing this state is proposed. In the calculation, contributions of operators up to dimension six are included in the operator product expansion （OPE）, as well as terms which are linear in the strange quark mass ms. We find ml-＋ = （4.82 ~ 0.19） GeV, which is not compatible with the X（4350） structure as a 1-＋ tetraquark state. Finally, we also discuss the difference of a four-quark state＇s mass whether the state＇s interpolating current has a definite charge conjugation.     

Semileptonic bc to cc and bb to bc baryon decays and heavy quark spin symmetry

We study the semileptonic decays of the lowest-lying bc baryons to the lowest-lying cc baryons （Ξ （＊） bc → Ξ （＊） cc and Ω （ ＊） bc → Ω （＊） cc ）,in the limit m b,m c Λ QCD and close to the zero recoil point.The separate heavy quark spin symmetries make it possible to describe all these decays using a single form factor.We also show how these constraints can be used to test the validity of different quark model calculations.bb to bc baryon decays are also discussed.     

Top pair production in the littlest Higgs model with T-parity

In the framework of the littlest Higgs model with T-parity, we study the top pair production at the next generation colliders like LHC and ILC. We find that the order O（αs） corrections to the standard model top pair production cross section at LHC can be very small and the magnitude is below 1%. However, the magnitude of corrections to the standard model top pair production rate at ILC may be over 5% for reasonable values＇of the parameters. Besides this, the corrections to the asymmetry ALR（tt） may be more sizable. Therefore, the top pair production at ILC may serve as a probe of the littlest Higgs model with T-parity, especially the asymmetry ALR（tt）.     

Axial charges of N（1535） and N（1650） in two-flavor lattice QCD

We show the lattice QCD results on the axial charge gAN＊-N＊ of negative parity nucleon resonances, N＊（1535） and N＊（1650）, which are key clues to the chiral structure in baryon sector. The measurements are performed with up and down dynamical quarks employing the renormalization-group improved gauge action at β=1.95 and the O（a） improved clover quark action with the hopping parameters, κ=0.1375, 0.1390 and 0.1400. In order to properly separate signals of N＊ （1535） and N＊ （1650）, we construct 2 × 2 correlation matrices and diagonalize them. Wraparound contributions in the correlator, which can be another source of signal contaminations, are eliminated by imposing the Dirichlet boundary condition in the temporal direction. We find that the axial charge of N＊ （1535） takes small values as gAN＊N＊-O（0.1）, whereas that of N＊ （1650） is about 0.5, which is found independent of quark masses and consistent with the predictions by the naive nonrelativistic quark model.     

N＊（1535） contribution in pp →ppη＇ and pn →dφ

In an effective Lagrangian model we find that the N＊（1535） resonance contribution might be important to the interpretation of the present data of the pp →ppη＇ and pn →dφ reactions. The strong coupling strength of N＊ （1535） to η＇ and φ are indicated, and the possible implication to the intrinsic component of N＊（1535） is explored. These results may provide hints to the real origin of the OZI rule violation. It is stressed that further measurements could be performed at China. the Cooling Storage Ring （CSR） at Lanzhou of     

Quenched Charmed Meson Spectra Using Tadpole Improved Quark Action on Anisotropic Lattices

Charmed meson charmonium spectra are studied with improved quark actions on anisotropic lattices. We measured the pseudo-scalar and vector meson dispersion relations for four lowest lattice momentum modes with quark mass values ranging from the strange quark to charm quark with three different values of gauge coupling β and four different values of bare speed of light v. With the bare speed of light parameter v tuned in a mass-dependent way, we study the mass spectra of D, Ds, ηc, D^＊, D^＊s and J/ψ mesons. The results extrapolated to the continuum limit are compared with the experiment, and a qualitative agreement is found.     

Is Kano-Nucleon Interaction Consistent with Pentaquark θ^＋

The quark-delocalization colour-screening model is employed to calculate the effective potential between nucleon and kaon. The results show that the potentials are attractive in the I = 0 channel and repulsive in the I = 1 channel. The interactions are very weak between K^＋n or K^0p due to the cancellation between I = 0 and I = 1. It is possible to have a high s-wave resonance （1615 MeV）, but the width may be too wide to be observed in the experiments.     

Structure of Di-Ω Dibaryon

Previously, we extended our chiral SU（3） quark model to include the coupling between the quark and vector chiral fields [Nucl. Phys. A 727（2003）321]. Here we further study the structure of （ΩΩ）ST=oo dibaryon in the extended chiral SU（3） quark model by solving a resonating group method equation. The vector meson exchanges effect, hidden colour channel and colour screening effect are investigated, respectively. The results show that the （ΩΩ）ST=oo system is still the deeply bound state in the extended chiral SU（3） quark model in which the vector meson exchanges control the short-range quark-quark interaction, which is similar to the results obtained from the chiral SU（3） quark model. When the model space is enlarged by including the hidden colour channel, it is found that the energy of the hidden colour state ｜CC〉str=-6,ST=oo is much higher than that of the （ΩΩ）ST=oo state, thus the CC channel has little effect on the binding energy of （ΩΩ）ST=oo state. When the error function confinement potential is considered, the bound state property would not change largely. Fhrther, scalar meson mixing is considered. No matter whether θs= -18° or ideal mixing is taken, （ΩΩ）ST=oo state is still a bound state.     

Ds1（2536）^＋ decays and the structure of P-wave charmed strange mesons

We calculate the D s 1 （2536） ^＋ decays into D＊K channels,including the decay D s 1 （2536） ＋ → D ＋ π-K ＋ through a virtual D＊0 in a constituent quark model.Widths and S/D amplitudes ratio are in agreement with the recent Belle and BABAR data,being the results sensitive to 1 P 1 and 3 P 1 mixture.     

The mass effect of the quark phase transition in supernova core

Constituent quark mass model is adopted as a tentative one to study the phase transition between two-flavour quark matter and more stable three-flavour quark matter in the core of supernovae. The result shows that the transition has a significant influence on the increasing of the core temperature, the neutrino abundance and the neutrino energies, which contributes to the enhancement of the successful probability of supernova explosion. However, the equilibrium values of these parameters （except the temperature） from the constituent quark mass model in this work are slightly bigger than those obtained from the other model. And we find that the constituent quark mass model is also applicable to describing the transition in the supernova core.