手征胶子修正夸克平均场模型

这项工作利用考虑π介子与胶子效应的夸克平均场模型研究原子核结构的基本性质。在夸克平均场中,核子由三个束缚在谐振子势场中的组分夸克构成。描述强相互作用的量子色动力学必须满足手征对称性,此外夸克之间也需要通过交换胶子相互作用。因此,在夸克平均场模型中,对利用夸克势获得的核子质量考虑π介子修正与胶子修正。通过少数稳定有限核的结合能与半径实验值确定模型中的未知参数,获得了一组夸克平均场相互作用参数,QMF-NK。利用该组参数计算40Ca和208Pb的电荷密度分布,发现与实验值符合很好。随后获得了与经验值一致的对称核物质的饱和性质。包含π介子修正和胶子修正的夸克平均场模型能够更好地描述有限核和核物质的性质。The basic properties of nuclear structure are studied within the quark mean field (QMF) model by taking the effects of pions and gluons into account. In QMF, the nucleon is made up of three constituent quarks confined by a harmonic oscillator potential. The quantum chromodynamics describing the strong interaction must satisfy the chiral symmetry and quarks interact with each other through exchange of gluons. Therefore pion correction and gluon correction are included in the nucleon mass obtained by using quark confinement potential in quark mean field model. We determine the unknown parameters in the model by fitting the experimental data of the binding energies and radii of several stable finite nuclei and obtain a set of parameters of quark mean field interaction, named QMF-NK. The charge density distributions of 40Ca and 208Pb are calculated, which are in good agreement with the experimental data. Later the saturation properties of symmetric nuclear matter which are consistent with the empirical data are obtained. With the pion and gluon corrections, the QMF model could treat finite nuclei and nuclear matter better.     

夸克模型中的等效介子交换势与NN散射

用单胶子交换正反夸克对产生模型给出的等效单单介子交换势和等效两π介子交换势计算了NN散射S分波的相移,给出了部份核力的中程吸引的特性.     

由单胶子交换的正反夸克对产生模型研究ρ,K介子的强作用衰变

用单胶子交换正反夸克对产生模型研究了ρ介子到2π介子和K*到Kπ衰变宽度,理论与实验值基本相符.     

核子–核子散射过程的研究和矢量介子交换势

在推广的手征SU(3)夸克模型下讨论了核子–核子散射过程和矢量介子交换势.给出了赝标π介子和矢量ρ和ω介子的GCM中心力的交换势和NN散射14个分波的相移.研究表明,矢量介子交换势可以替代单胶子交换势以解释核力的短程排斥.     

核力的手征夸克-孤子模型理论

本文简短地描述了含单胶子交换的手征夸克孤粒子模型;将此孤粒子模型里所确定的夸克-胶子耦合常数及所解得的夸克波函数,输入到相对论的两夸克集团理论,研究了两核子系统问题.本文完整地考虑了夸克交换核中的动能和相对运动能量项,由此改进了~3S_1道和~1S_0道的相移.相移与Arndt等人的实验相移基本一致.计算结果表明,单胶子交换和夸克交换提供短程排斥势,手征场则提供了中、长程吸引势.     

Spectra of charmed and bottom baryons with hyperfine interaction

Up to now,the excited charmed and bottom baryon states have still not been well studied experimentally or theoretically.In this paper,we predict the mass of ?*b,the only L=0 baryon state which has not been observed,to be 6069.2 Me V.The spectra of charmed and bottom baryons with the orbital angular momentum L = 1 are studied in two popular constituent quark models,the Goldstone boson exchange(GBE) model and the one gluon exchange(OGE) hyperfine interaction model.Inserting the latest experimental data from the "Review of Particle Physics",we find that in the GBE model,there exist some multiplets(Σc(b),Ξ c(b)and ?c(b)) in which the total spin of the three quarks in their lowest energy states is 3/2,but in the OGE model there is no such phenomenon.This is the most important difference between the GBE and OGE models.These results can be tested in the near future.We suggest more efforts to study the excited charmed and bottom baryons both theoretically and experimentally,not only for the abundance of baryon spectra,but also for determining which hyperfine interaction model best describes nature.     

双胶子交换模型中J/ψ的衍射产生

利用双胶子交换模型并结合重夸克偶素的色八重态产生机制,计算了π与p碰撞过程中J/ψ的衍射产生总截面.结果发现:随着质心系能量的增加,J/ψ衍射产生的总截面逐渐增大;并且,不同的π介子中的胶子分布函数给出的总截面偏离也逐渐加大.计算结果与未来的实验数据比较,可以检验π介子中的胶子分布函数及双胶子交换模型.     

Structures of（ΩΩ）0＋and（[1]Ω）1＋in Extended Chiral SU（3） Quark Model

The structures of (ΩΩ)0 and ([1]Ω)1 are studied in the extended chiral SU(3) quark model in which vector meson exchanges are included. The effect from the vector meson fields is very similar to that from the one-gluon exchange (OGE) interaction. Both in the chiral SU(3) quark model and in the extended chiral SU(3) quark model,di-omega (ΩΩ)0 is always deeply bound, with over one hundred MeV binding energy, and ([1]Ω)1 ‘s binding energy is around 20 MeV. An analysis shows that the quark exchange effect plays a very important role for making di-omega (ΩΩ)0 deeply bound.     

洛伦兹规范条件下对单胶子夸克势的QCD非微扰修正形式

在洛伦兹规范条件下,导出了具有平移不变性的双胶子两点函数真空平均值.利用所获得的双胶子真空期待值,给出了对微扰单胶子交换夸克–夸克势、夸克–反夸克对湮没和夸克–反夸克对激发势的最低阶非微扰QCD修正形式.     

核力的手征夸克-孤子模型理论

本文简短地描述了含单胶子交换的手征夸克孤粒子模型;将此孤粒子模型里所确定的夸克-胶子耦合常数及所解得的夸克波函数,输入到相对论的两夸克集团理论,研究了两核子系统问题.本文完整地考虑了夸克交换核中的动能和相对论运动能量项,由此改进了³S₁道和¹S₀道的相移.相移与Arndt等人的实验相移基本一致.计算结果表明,单胶子交换和夸克交换提供短程排斥势,手征场则提供了中、长程吸引势.     

Different Interaction Models in Strong Decays of Negative Parity N* Resonances Under 2 GeV

In this paper, by using harmonic-oscillator wave functions of different interaction models, i.e. OPE (one-pion-exchange model), OPsE (only pseudoscalar meson exchange model), the extended GBE (Goldstone-boson-exchange model including vector and scalar mesons), and OGE (one-gluon-exchange model), we calculate and compare the strong decays of negative parity N^* resonances under 2 GeV. We find that the conventional mixing angles are correct, and GBE and OGE are obviously superior to OPE and OPsE.     

Nonlocality effects in the phase diagram of neutral quark matter

We construct phase diagrams of two-flavor quark matter under compact star constraints for two nonlocal, covariant quark models (instanton liquid and one-gluon exchange (OGE) inspired) within the mean field approximation and compare the results for different diquark coupling strengths. For the OGE model, stable hybrid stars with quark cores are obtained. The text was submitted by the authors in English.     

One-gluon exchange corrections to magnetic moments of baryons

One-gluon exchange (OGE) corrections to the magnetic moments of the octet baryons are studied in the bag model. It is clarified that OGE resolves a problem of μ(Λ) and μ(Ξ^?) in previous quark model calculations and also improves an overall agreement between theory and experiment.     

Forward reactions and the exploration of particle dynamics

Since the polarization structure of reactions in the collinear directions is greatly simplified, since reactions at very high energies tend to be predominantly close to collinear, and since the one-particle exchange mechanisms are more pronounced in the forward direction, tests of one-particle-exchange (OPE) mechanisms are formulated for collinear reactions. The number of amplitudes are derived for a reaction with arbitrary spins, and examples for the practically occurring cases are given. The results are applied to the reaction 1/2+1/21+1 and in particular ton+pd+ (or to its inverse). A detailed procedure is outlined for a step-by-step testing of the various OPE processes in this reaction through a series of polarization experiments. In particular, the tests can separate out theJ=0 andJ=1/2 OPE processes.     

Relativistic effects and the constituent quark model of heavy quarkonia

Charmonium \(c\bar c\) and bottomonium \(b\bar b\) are investigated in the framework of a constituent quark model. A scalar confining and a one-gluon exchange (OGE) potential are used in a nonrelativistic reduction to order (p/m)². Therefore the model includes spin dependent as well as spin independent terms. Their influence on the meson mass spectra and decay widths is analysed. We find that the experimental spectra can be reproduced by using a full model as well as by using a reduced version neglecting the spin independent terms. For both versions we calculate leptonic and radiative decay widths including relativistic corrections for the current operators. We find that for leptonic decays inclusion of all terms of the OGE potential gives better results than the non-relativistic formulas. For radiative transitions relativistic corrections are important.     

Electroproduction of ω-mesons as a test of the ϱωπ-vertex

A simple model for electroproduction of ω-mesons is presented. The non-diffractive part is described by elementary OPE without corrections, combined with vector-meson dominance. For the diffractive production amplitudes we assume helicity conservation in the direct channel. We discuss the differential cross section and the spin-density matrix of the ω-mesons, particularly emphasizing the dependence on the mass of the virtual photon and the possibility to test the mass-dependence of the ?ωπ coupling constant.     

SPIN-SPIN FORCE EWHANCEMENT FOR QUARKS

We argue that in addition to OGE potential suggestedr by the lowest order QCD a spin-spin force enhancement seems to be needed and that aside from the pseudoscalar e.g pion exchange,the axial vector or tensor exchanges may greatly enhance the spin-spin force.     

The current product expansion of the two-quark process at the twist-four level

The operator product expansions of the two-quark process for electromagnetic and weak currents are calculated at the twist-four level in the leading order of the running coupling constant. Operators with contracted derivatives but without gluon field strengths F_μν are chosen as a basis of the OPE. This greatly simplifies the calculation without losing practicality. The results are expressed using the invariant amplitudes of the matrix elements of operators.