Mesons in the Constituent Quark Model

The quark-antiquark （q^-q） spectrum is studied by solving the Schrōdinger equation in the framework of nonrelativistic constituent quark model. An overall good fit to the experimental data of meson is obtained. The interactions between quark and antiquark consist of quadratic colour confinement-exchange, one-gluon-exchange, and Goldstone-boson-exchange potentials.     

Scalar Mesons in the Light-Front Quark Model

We discuss light-front quark-model calculations of the scalar meson spectrum and decays.     

夸克模型下的轻介子质量谱

最近,文献[1]将辅助场方法应用于准相对论性夸克模型中,获得了一个解析的非奇异轻介子质量公式。本文将这种方法推广到奇异轻介子的情况,得到了一个味道依赖的轻介子质量公式。结果表明,质量公式预言的低激发态质量谱与实验值吻合良好,平均误差在30 MeV左右。质量公式预言的高激发态质量谱和其他文献（特别是弦模型）的计算相比,也符合较好。Recently, with the help of auxiliary field method, Ref.[1] obtains an analytical mass formula for nonstrange light mesons in quasi-relativistic quark model. In this work, we generalize this method to the case of strange light mesons, and obtain a mesonic mass formula which is flavor-dependent. The results show that the mass of low excitations given by the mass formula are in good agreement with the experimental data and the average error is around 30 MeV. Our mass predictions for the high states also agree well with the other calculations in the literatures, particularly, the string model calculations.     

相对论夸克模型中底奇异介子的辐射衰变(英文)

系统地研究了相对论夸克模型框架下的底奇异介子的辐射衰变。给出了底奇异介子E1 和M1 辐射衰变分宽度。这些结果表明,大多数电偶极辐射衰变宽带能达到数个keV,大多数磁偶极辐射衰变宽度小于1 个keV,这为实验上通过辐射衰变寻找底奇异介子提供了理论依据。建设中的Belle II 上的实验可以进一步验证我们的结果。We systematically study the radiative transitions of bottom-strange mesons in the framework of the relativistic constituent quark model. The partial widths of the E1 and M1 decays are predicted. The results predict that most of E1 decay widths are several keV and most of M1 decay widths are less than 1 keV,which give a roadmap of searching for the higher bottom-strange mesons via radiative decays. The experimental searches by the forthcoming Belle II can in turn provide further tests to our result in the present work.     

Weak Decays of D and Ds Mesons in a Relativistic Quark Model

The transitions of D and D_s, mesons to light vector states are studied in a relativistic constituent quark model based on the Bethe-Salpeter formalism. The form factors are calculated, and the branching fractions for both semileptonic and nonleptonic decays are given. The results show that the form factors for these transitions deviate substantie from the request of heavy quark symmetry. All the branching ratios for D and D_s semileptonic decays are found to be consistent with data, whereas the calculations of nonleptonic D and D_s decays under the factorization assumption do not agree with experiments. This confirms the conjecture that the factorization scheme is much less applicable in D and D_s decays than in B and B_s decays.     

夸克和弦模型中非奇异轻介子的类雷吉谱(英文)

本工作重新考察了相对论弦模型和准相对论夸克模型中轻介子的类雷吉谱。基于辅助场技术,提出了非奇异轻介子的一个解析质量公式,由此推导出了一个准线性的Regge-Chew-Frautschi轨迹关系,并将此关系用相应介子的实验数据（PDG）进行了检验。检验结果表明,和实验观测数据比较,夸克模型对介子质量的预言与弦模型的相符,但在角动量较大时,夸克模型的预言稍微优于弦模型。We revisit the Regge-like spectra of light mesons in the relativistic string model and the simirelativistic quark model. An analytical mass formula is proposed for light mesons based on the auxiliary field technique, and a quasi-linear Regge-Chew-Frautschi plot with flavor dependence is derived and verified with the experimental data(PDG) for light mesons.The results show that the quark model predictions for meson masses agree with those of the string model, but are slightly better when the angular momentum is relatively large as compared with the observed data.     

Color Superconductivity in Cold Dense Quark Matter

We investigate the phase structure of color superconducting quark matter at intermediate densities for two- and three-flavor systems. We thereby focus our attention on the influence of charge neutrality conditions as well as -equilibrium of the different phases. These constraints are relevant in the context of quark matter at the interior of compact stars. We analyze the implications of color superconductivity on compact star configurations using different hadronic and quark equations of state.Presented at the 15th Indian-Summer School of Physics: Understanding Dense Matter, Prague, Czech Republic, 27 August–1 September, 2003.     

夸克模型中的Dsj(2317),Dsj(2460)衰变

用夸克模型结合D_s,D_s^*, 讨论窄共振态D_sj^*(2317),D_sj(2460). 除η－π⁰混合角由D^*_s衰变宽度给出, 所有的参数均取自Godfrey和Isgur的夸克模型. 得到的电磁衰变宽度与实验数据和其他作者的结果相一致. 但是, 与现有的实验结果比较, D_sj^*(2317), D_sj(2460)的π介子衰变宽度要小一个数量级. 我们怀疑简单的手征夸克-π轴矢相互作用的哈密顿量不适合于D_sj^*(2317), D_sj(2460)的强衰变.     

Unquenching the Quark Model

The formalism for a new generation of unquenched quark models for baryons in which the effects of quark?Cantiquark pairs are taken into account in an explicit form via a microscopic, QCD-inspired, quark?Cantiquark creation mechanism, is presented. As an application the quark?Cantiquark contribution to the spin of the proton and the ??⁺ is discussed. Finally the strangeness radius of the ??⁺ in the closure limit is calculated.     

Sum Rules in the Quark Model

With the help of various sum rules we look into the spin-isospin excitations in nuclei within a framework of the quark model. The effect of Pauli correlations is explicitly taken care of. In agreement with the experiments we find negligible amount of M1 strength in heavy nuclei. This is explained in terms of the Fermi gas model.     

Tetraneutron in the Chiral Quark Model

The tetraneutron state is studied in the framework of the chiral quark model with tetrahedron configuration. The universal attraction property of σ-meson exchange leads to a strong attraction in the effective potential of the system. It is possible to form a bound state. For comparison, the naive quark model is also employed to carry out the calculation. A weak attraction, which is too weak to bind the system, is obtained.     

Discussion of the 3P0 Model Applied to the Decay of Mesons into Two Mesons

 The model for the decay of a meson into two mesons is revisited. In particular, the formalism is extended in order to deal with an arbitrary form for the creation vertex and with the exact meson wave functions. A careful analysis of both effects is performed and discussed. The model is then applied to a large class of transitions known experimentally. Two types of quark-antiquark potentials have been tested and compared. Received July 9, 1999; revised September 10, 1999; accepted for publication October 27, 1999     

Decays of Dsj*(2317) and Dsj(2460) Mesons in the Quark Model

We study the decay widths of the narrow resonances D_sj^*(2317) and D_sj(2460) in the chiral quark model, together with the well-known D^* and D_s^* mesons. All the parameters in our calculation are taken from Godfrey and Isgur's quark model except the π⁰－η mixing angle which is fixed by the D_s^* decay widths. The calculated electromagnetic decay widths agree with those from other groups and the experimental data available quite well. However, the pionic decay widths of D_sj(2317) and D_sj(2460) are too small to fit the experimental data. We suspect that the simple chiral quark pion axial-vector interaction Hamiltonian is not suitable for hadron strong decays of D_sj(2317) and D_sj(2460).     

Chiral Extension of the Quark Model

The chiral extension of the minimal standard model makes quarks with two chiralities present parallelly. Some interesting questions, such as the possibility of that the leptons are made of additional leptonic quarks and the proton decay are discussed.     

在具有伸缩子的QCD势模型中的重介子

从伸缩子–胶子有效耦合理论得到的重夸克–反夸克势模型出发,计算了重介子的自旋平均能谱及轻子衰变和辐射跃迁宽度,并与Cornell势模型所得到的相应结果作了比较.结果表明,新的重夸克势的计算结果与重介子的实验数据更好地符合,而且估计的伸缩子质量5?7MeV很好地位于有关伸缩子质量的其他理论途径所估计的范围之内.     

Superconductivity in the Two-Dimensional Hubbard Model

It is shown that the existence of d-wave superconductivity in the two-dimensional Hubbard model close to half-filling can be inferred from a renormalization group analysis at one-loop level.     

奇异夸克物质的夸克质量密度温度相关模型(英文)

在夸克质量密度相关模型处理奇异夸克物质滴时 ,会发现其半径随温度增加而变小 .为克服这一困难 ,我们通过使口袋常数 B温度参数化 ,引入了夸克质量密度温度相关模型 .在这一模型中 ,B=B0 [1 - a(T/Tc) +b(T/Tc) 2 ],文章中讨论了参数 a,b的取法. It is found that the radius for a stable strangelet is a decreasing function of temperature in quark mass density- dependent model. To overcome this difficulty, we extend this model to quark mass density- and temperature- dependent model in which the vacuum energy density at zero baryon density limit B depends on temperature. An ansatz B=B 0[1-a(T/T c )+b(T/T c ) 2] is introduced and the regions for the best choice of the parameters are studied.     

对于组分夸克模型的几点评注

根据现有的格点QCD结果和手征对称自发破缺理论研讨了组分夸克模型中夸克囚禁和夸克介子耦合方案.指出了两体囚禁势不能直接推广应用于多夸克系统,σ介子作为双π交换的等效描述只能用于u,d夸克,不能用于s夸克.