由QCD求和规则计算s夸克质量

简要回顾了量子色动力学求和规则在计算s夸克质量方面的应用.结合Dominguez,Gend和Paver的工作,重新考虑渐近自由阈以下的谱函数后,计算了s夸克的质量,得到s夸克的跑动质量(-m)s(1 GeV)=219 MeV.讨论了影响计算结果精度的可能因素.     

夸克物质中的色超导性理论简介(英文)

夸克-夸克通过单胶子交换的相互作用在其反对称态上是相互吸引的,在致密夸克物质里,这种吸引相互作用会导致费米面上的双夸克凝聚,这就是所谓的夸克配对或色超导现象。本文介绍了夸克配对或色超导现象的基本知识和一些新进展。色超导是一个对称性自发破坏现象,有非常丰富的破缺方式,我们介绍了色超导对称性及其自发破坏模式的分析方法,介绍了怎样计算色超导体两个最基本的变量:能隙和迈斯纳质量。然后我们介绍了描述色超导现象的有效理论。最后是这些理论的一个应用,即计算色超导体里的中微子发射率以及其它输运性质。本文可以作为研究夸克物质理论的入门参考资料。     

夸克物质中的色超导性理论简介

夸克-夸克通过单胶子交换的相互作用在其反对称态上是相互吸引的,在致密夸克物质里,这种吸引相互作用会导致费米面上的双夸克凝聚,这就是所谓的夸克配对或色超导现象。本文介绍了夸克配对或色超导现象的基本知识和一些新进展。色超导是一个对称性自发破坏现象,有非常丰富的破缺方式,我们介绍了色超导对称性及其自发破坏模式的分析方法,介绍了怎样计算色超导体两个最基本的变量：能隙和迈斯纳质量。然后我们介绍了描述色超导现象的有效理论。最后是这些理论的一个应用,即计算色超导体里的中微子发射率以及其它输运性质。本文可以作为研究夸克物质理论的入门参考资料。     

含有四个夸克或更多夸克的奇特粒子

<正>在粒子物理的所谓"标准模型"中发生强相互作用的基本粒子是带有分数电荷的夸克,这些夸克被电中性的类似光子的"胶子"捆绑在一起形成强子(包括重子和介子)。目前标准模型中包含6种不同"味道"的夸克:上夸克(u)、下夸克(d)、奇异夸克(s)、粲夸克(c)、底夸克(b)和顶夸克(t);它们各自的反粒子(反夸克)被标志为、d、、、、。每一种味道的夸克又带有强作用的3种不同的"色荷"之一的"色荷"。之所以称之为"色荷"是因为强相互作用将这些带色荷的夸克束缚在一起形成强子的法则很容易让我们类比到对颜色的感知。     

重子中七夸克成分qqq(qˉq)2的低位能谱

在非相对论夸克模型内,利用手征超精细相互作用,把原来对五夸克系统qqqqˉq能谱的预言,扩展到了七夸克系统qqq(qˉq)2的基态和轨道第一激发态能谱的计算,所使用的参数也是来自于五夸克系统.预言了最低七夸克态的能量大约是2.1 GeV,自旋-宇称是JP=1也存在一些三夸克系统和五夸克系统,所以能量在2 GeV以上的重子激发态可能是这3种夸克成分的混合.+或者JP=1?.由于在这个能区22     

Σ-N相互作用的研究及_Σ~4He结合能的计算

基于SU(3)夸克模型,用共振群方法研究了两种理论下的Σ-N相互作用,得到了它们的相互作用非定域位以及Σ超子与3He壳心核的相互作用势,并在此基础上计算了4ΣHe基态结合能。计算结果表明,SU(3)夸克模型能较好地描述两种理论下的Σ-N相互作用及Σ超子与3He壳心核的相互作用势,同时由其得到的Σ4He基态结合能也与实验值基本相吻合。     

夸克-介子耦合模型

对夸克-介子耦合模型的研究进展及现状进行了简述.在此基础上,利用非拓扑孤子袋模型的思想和改进的夸克质量密度相关(IQMDD)模型,考虑夸克之间的排斥作用而加入ω介子,称为IQMDD-Ⅰ模型,得到了基态波函数和介子场满足的方程.利用平均场近似方法,通过得到的基态夸克波函数计算了核子的均方根半径和磁矩等可观测量,其结果与实验值吻合得较好.     

Σ-N相互作用的研究及 4ΣHe结合能的计算

基于SU(3)夸克模型， 用共振群方法研究了两种理论下的Σ-N相互作用， 得到了它们的相互作用非定域位以及Σ超子与3He壳心核的相互作用势， 并在此基础上计算了4ΣHe基态结合能。 计算结果表明， SU(3)夸克模型能较好地描述两种理论下的Σ N相互作用及Σ超子与3He壳心核的相互作用势， 同时由其得到的 4ΣHe基态结合能也与实验值基本相吻合。     

基态八重态重子质量的手征描述

质量作为物质最基本的属性,其起源一直是物理学研究的根本问题之一。根据物质层次的 划分,理解可见宇宙物质（能量）组成的关键在于理解核子（基态重子）的质量。现代粒子物理与 原子核物理研究指出,基态重子质量的绝大部分来自强相互作用。然而,由于色禁闭现象,强相互 作用的基本理论–量子色动力学–在低能区无法解析求解,导致很长一段时间里对基态重子质量的 研究不得不借助于各种唯象模型。二十一世纪以来,随着计算机运算能力的发展和算法的持续改 进,格点量子色动力学模拟取得了令人瞩目的成绩,使得人类从第一原理出发计算基态重子的质 量,进而定量地理解质量的起源成为可能。另一方面,受到计算资源的限制,目前绝大部分格点 量子色动力学模拟必须采用比物理值大的轻夸克质量、不足够大的盒子体积和不足够小的格点间 距。因而,为了从格点量子色动力学模拟中提取感兴趣的观测量的物理值,必须对格点数据进行 如下三种延拓：手征延拓将轻夸克质量延拓到物理值（即mq ! mphys: q ）,有限体积修正将有限的四 维空间延拓到无穷大（即V = L4 ! 1）,连续性延拓将有限格点间距延拓到零（即a ! 0）。手征 微扰理论为开展这些延拓提供了必要的理论基础。作为量子色动力学的低能有效理论,手征微扰 理论原则上可以模型无关地描述强相互作用物理。但随着手征阶数的升高,仅仅依靠实验数据无 法完全确定理论中未知的低能常数。高统计量的格点量子色动力学模拟数据的出现为解决这一难 题提供了新的思路,从而使得基于高阶手征微扰理论的研究成为可能。本文将简要介绍当前基于 协变重子手征微扰理论对基态八重态重子质量及格点量子色动力学模拟数据的研究。     

铈原子基态的理论研究

在有心力场近似和组态相互作用理论框架下,通过对电子波函数、各壳 层上电子的束缚能、半径、总束缚能的分析和计算,研究了Ce原子的可能的基组态及其基态 时的原子态。研究结果表明：基组态为4f5d,基态原子态为1G4。     

A string-breaking model of heavy meson decays

Within QCD, heavy quarkonia are viewed as a quark antiquark pair bound by a narrow chromoelectric flux tube. This flux can create light quark antiquark pairs accounting for the decay into mesons with heavy quantum numbers. This model is shown to be as consistent with current data on charmonium decays intoD-meson pairs and upsilon decay to \(B\bar B\) , as is the physically less appealing³ P ₀ model.     

Quark Mass Functions and Pion Structure in Minkowski Space

We present a study of the dressed quark mass function and the pion structure in Minkowski space using the covariant spectator theory. The quark propagators are dressed with the same kernel that describes the interaction between different quarks. We use an interaction kernel in momentum space that is a relativistic generalization of the linear confining \({q\bar{q}}\) potential and a constant potential shift that defines the energy scale. The confining interaction has a Lorentz scalar part that is not chirally invariant by itself but decouples from the equations in the chiral limit and therefore allows the Nambu–Jona–Lasinio mechanism to work. We adjust the parameters of our quark mass function calculated in Minkowski-space to agree with LQCD data obtained in Euclidean space. Results of a calculation of the pion electromagnetic form factor in the relativistic impulse approximation using the same mass function are presented and compared with experimental data.     

Probing Quark Loop Effects on Dressed Gluon Propagator

We study the quark loop effects on the dressed gluon propagator and also on the quark propagator itself. We find that the gluon propagators are different in two phases. The quark mass effects on the gluon propagator are small but not negligible. We also study the current quark mass dependence on the bag constant.     

Equation of state in hybrid stars and the stability window of quark matter

Properties of hybrid stars with a mixed phase composed of asymmetric nuclear matter and strange quark matter are studied. The quark phase is investigated by the quark quasiparticle model with a self-consistent thermodynamic and statistical treatment. We present the stability windows of the strange quark matter with respect to the interaction coupling constant versus the bag constant. We find that the appearance of the quark–hadron mixed phases is associated with the meta-stable or unstable regions of the pure quark matter parameters. The mass–radius relation of the hybrid star is dominated by the equation of state of quark matter rather than nuclear matter. The contour plots of the maximum mass of the hybrid star are shown in the plane of the coupling constant and the bag constant.     

Chiral symmetry breaking and pion properties at finite temperatures

Spontaneous and explicit chiral symmetry breaking is analyzed in Coulomb gauge QCD at finite temperatures, using an instantaneous approximation for the quark interaction and incorporating confinement through a running coupling constant. The thermodynamics of the quarks is treated approximatively by assuming that the momentum-dependent constituent quark mass sets the scale for thermodynamic fluctuations of colour singlet excitations. We investigate the class of a temperature independent and a temperature dependent interaction between quarks. In the chiral limit both temperature independent and a smooth temperature dependent interaction yields a second order chiral phase transition with critical exponents close to the values for a BCS super-conductor. For explicit chiral symmetry breaking we find a nearly constant pion mass below the transition temperature, but a strongly overdamped mode above. For a first order deconfining transition in the gluonic sector also the quark sector shows a first order chiral phase transition. The relevance of our results for relativistic heavy ion collisions is briefly discussed.     

Hadron resonance gas and nonperturbative QCD vacuum at finite temperature

Nonperturbative QCD vacuum with two light quarks at finite temperature was studied in a hadron resonance-gas model. Temperature dependences of the quark and gluon condensates in the confined phase were obtained. It is shown that the quark condensate and one-half (chromoelectric component) of the gluon condensate are evaporated at the same temperature corresponding to the quark-hadron phase transition. With allowance for the temperature shift of hadron masses, the critical temperature was found to be T _c ?190 MeV.     

An application of a heavy quark bag model to non-leptonic decays of charmed baryons

Non-leptonic decays of lower mass charmed baryons are calculated by employing the QCD corrected weak Hamiltonian and wave functions of a heavy quark bag model. Baryon matrix elements of the parity violating part of the charmchanging weak Hamiltonian are included, too. The results for the partial widths Γ and asymmetry parameters α are compared with the results of other models and with experiments.     

质量密度相关模型研究CFL奇异夸克物质性质

在质量--密度相关模型下研究了CFL奇异夸克物质, 并将结果与传统的袋模型结果进行比较. 两个模型均表明, 在合理的参数范围内, CFL相比正常核物质更稳定. 然而, 低密度时声速的行为完全相反, 这使得CFL夸克星的最大质量在质量-密度相关模型下比袋模型大.     

Potential of heavy quarks in the static limit of QCD

The potential of static quarks that is consistent both with the three-loop QCD running coupling constant, the two-loop perturbative matching of the \(\overline {MS} \) and V schemes being taken into account here, and with the regime of quark confinement at long distances is derived on the basis of the procedure and arguments proposed by Richardson, Buchmüller, and Tye. Applications of this approach are discussed for the masses of heavy quarks, for the mass spectra of heavy quarkonia, and for the leptonic widths of vector states.