物质结构在夸克-轻子层次上的动力学规律和研究发展趋势

文章综述了粒子物理中标准模型理论的历史发展、面临挑战以及未来的发展趋势.目前阶段物质结构最小组成单元是夸克和轻子,量子色动力学是描述夸克-胶子之间强相互作用的基本理论,它具有渐近自由和夸克禁闭的特点.量子色动力学和电弱统一理论一起构成粒子物理中标准模型理论.标准模型理论成功同时也面临两大挑战:对称性破缺的本质和夸克禁闭难题,这意味着标准模型理论需要发展和突破.人们期望粒子物理学、天文学和宇宙学交叉发展联手解决物质结构和早期宇宙研究中面临的难题,最终揭示超出标准模型的新物理规律.     

核子(强子)结构和性质的QCD研究

核子 (强子 )是夸克、胶子的束缚态 ,由量子色动力学 QCD描述。由于 QCD的基本特性(高能标度下的渐近自由、低能标度下色禁闭及动力学手征对称性破缺 ) ,对核子 (强子 )结构和性质的 QCD图象是标度相关的 .在高能标度下描述强子的是与探测强子结构的硬过程相联系的QCD部分子模型 .强子的夸克、胶子结构信息通过 QCD部分子求和规则得到 .QCD微扰论是适用的理论 .在低能标度时 ,必须发展 QCD非微扰途径来描述核子 (强子 )物理 .这里简要地讨论各种非微扰途径 (格点 QCD、Dyson- Schwinger方程、有效场论、QCD求和规则 )的某些结果和进展 ,并指出 QCD真空结构在描述低能标度下强子物理中担任重要角色 . The nucleon (hadron) is the bound state of guarks and gluons, which is described by the quantum chromodynamics (QCD). Due to the basic properties of QCD (the asymptotic freedom at the high energy scale, the color confinement and the dynamical chiral symmetry breaking at the low energy scale), the QCD picture for the nucleon’s (hadron’s) structure and property is scale dependent. At high energy scale, the QCD parton model, which is relative to the hard process for testing the...     

规范场和爱因斯坦

文章讨论的主题是现代非亚贝尔规范场的理论思想．文章说明了这个理论思想是承传、推广和拓展了爱因斯坦的物理思想、目标和原则．规范场理论把爱因斯坦后半生努力奋斗而未能达到的目标提到现实，更加迫近和部分地圆了爱因斯坦的梦想。     

QCD真空凝聚和参数化的夸克传播子

基于整体色对称模型,用完全穿衣服参数化的夸克传播子研究了量子色动力学(QCD)真空的性质,预言了各种表征QCD真空的凝聚值.其结果与其他唯象QCD理论模型的预言是一致的.结果清楚地表明了参数化的夸克传播子是成功和可靠的.讨论了计算QCD真空凝聚值时积分截断参数的问题,提出了一个避免计算的结果对截断参数强烈依赖的物理方法.     

SU(N)亚夸克大统一模型中的Complementarity

本文将Complementarity应用于SU(N)亚夸克大统一模型,对亚夸克填充的SU(N)反常相消和渐近自由的各种表示进行分析,得到了满足Complementarity且有物理意义的SU(N)亚夸克大统一模型的最简单的表示;并预言夸克和轻子的代数g_N≥4.     

关于量子口袋动力学

将MIT边条件用于运动和变形中的口袋,讨论了口袋的动力学:包括变动中口袋内的单夸克和单胶子波函数;夸克──胶子场的量子化和由夸克──胶子系统推动的口袋运动的动力学及其量子化、发现:变动中的口袋内胶子场为符合MIT边条件必须包含纵场成份:夸克数算符和胶子数算符成为非(?)密的;口袋作为一个整体的动力学类似于强子场论的动力学,例如仍可沿用强子场论中的自由强子传播子而将强子内部的夸克──胶子结构反映到顶点的非定域化上,这样就完成了量子口袋动力学的一个理论框架,使得可以在按动力学结构将口袋模型重新参数化后,在夸克──胶子和强子的两个不同层次上统一研讨强子物理和核物理。 量子口袋动力学也是变动中的容器内的量子场沦以及容器内的场与容器表面耦合的量子理论的例子。     

动力学部分子模型在核子和冷核物质中的应用

本工作研究了自由核子和冷原子核物质的动力学产生的海夸克和胶子分布。在动力学部分子模型中,所有的海夸克和胶子纯粹来自DGLAP方程描述的QCD涨落过程,而较少的固有海夸克成分忽略不计。在$Q_0^2\sim 0.1$ GeV2标度,选择最大熵方法估计的三价夸克分布作为非微扰输入。使用了在低$Q^2$(本工作研究了自由核子和冷原子核物质的动力学产生的海夸克和胶子分布。在动力学部分子模型中,所有的海夸克和胶子纯粹来自DGLAP方程描述的QCD涨落过程,而较少的固有海夸克成分忽略不计。在$Q_0^2\sim 0.1$ GeV2标度,选择最大熵方法估计的三价夸克分布作为非微扰输入。使用了在低$Q^2$($<1$ GeV2)下饱和的跑动强耦合常数。关于原子核效应,考虑了核子变胖和部分子-部分子重组增强的影响。核子及冷核物质的动力学部分子分布均符合实验观测。应用预言的原子核部分子分布抽取得到部分子在穿过冷核物质时的能量损失。     

2004年诺贝尔物理奖介绍:渐近自由

描述粒子相互作用基本理论是标准模型，按照标准模型，强子是由夸克和反夸克通过色相互作用组成，色相互作用有一种特殊的性质：渐近自由，格罗斯、波利策和维尔切克由于确定地发现色相互作用的渐近自由性质获2004年诺贝尔物理奖。     

走向统一的自然力强力、弱力和电磁力的大统一(Ⅵ)

 标准模型,准确地讲,应是粒子物理标准模型。粒子物理是研究亚原子粒子的性质、结构及其在很高能量下相互转化的物理学分支学科。夸克模型的提出使人们认识到物质结构的基本组分是夸克和轻子,作用在它们之间的强力和弱电力可以分别用SU(3)规范场和SU(2)×U(1)规范场--相应的动力学分别是量子色动力学和弱电统一理论(或称量子味动力学)--来描述,分别通过胶子、中间玻色子(W^±和Z⁰)和光子来传递,于是SU(3)和SU(2)×U(1)规范场理论便构成了粒子物理标准模型。     

关于量子口袋动力学

将ＭＩＴ边条件用于运动和变形中的口袋，讨论了口袋的动力学：包括变动中口袋内的单夸克和单胶子波函数；夸克－胶子场的量子化和由夸克－胶子系统推动的口袋运动的动力学及其量子化，发现：变动中的口袋内胶子场为符合ＭＩＴ边条件必须包含纵场成份：夸克数算符和胶子数算符成为非厄密的；口袋作为一个整体的动力学类似于强子场论的动力学，例如仍可沿用强子场论中的自由强子传播子而将强子内部的夸克－胶子结构反映到顶点的非定域     

Color degrees of freedom in a quark-glue plasma at finite baryon density

We derive the color-singlet partition function for a quark-glue plasma with finite quark (baryon number) density by a projection method. Due to colorlessness there is a gradual “freezing” (reduction) of internal degrees of freedom as compared to the Stefan-Boltzmann limit. We find here that this non-perturbative effect is reduced by a finite quark density. A relation between the requirement of colorlessness of all physical states and QCD is proposed.     

Covariant QCD modeling of light meson physics

We summarize recent progress in soft QCD modeling based on the set of Dyson-Schwinger equations truncated to ladder-rainbow level. This covariant approach to hadron physics accommodates quark confinement and implements the QCD one-loop renormalization group behavior. We compare the dressed quark propagator, pseudoscalar and vector meson masses as a function of quark mass, and the → ππ coupling to recent lattice-QCD data. The error in the Gell-Mann-Oakes-Renner relation with increasing quark mass is quantified by comparison to the exact pseudoscalar mass relation as evaluated within the ladder-rainbow Dyson-Schwinger model.     

Chiral extrapolation, renormalization, and the viability of the quark model

The relationship of the quark model to the known chiral properties of QCD is a long-standing problem in the interpretation of low-energy QCD. In particular, how can the pion be viewed as both a collective Goldstone-boson quasiparticle and as a valence-quark-antiquark bound state? A comparison of the many-body solution of a simplified model of QCD to the constituent-quark model demonstrates that the quark model is sufficiently flexible to describe meson hyperfine splitting provided proper renormalization conditions and correct degrees of freedom are employed consistently.     

Relation Between the Pole Mass and MS Mass of Top Quark in Supersymmetric QCD

We discuss the relation between the pole mass and MS mass of top quark in the framework of the supersymmetric QCD.We find that the supersymmetric contributions are comparable to those of the standard model.     

On QCD sum rules of the Laplace transform type and light quark masses

We discuss the relation between the usual dispersion relation sum rules and the Laplace transform type sum rules in QCD. Two specific examples corresponding to the ?-coupling constant sum rule and the light quark masses sum rules are considered. An interpretation, within QCD, of Leutwyler's formula for the current algebra quark masses is also given.     

Jet energy loss and bulk parton collectivity in nucleus-nucleus collisions at RHIC

Nucleus-nucleus collisions at RHIC produce high temperature and high energy density matter which exhibits paxtonic degrees of freedom. We will discuss measurements of nuclear modification factors for light hadrons and non-photonic electrons from heavy quark decays, which reflect the flavor dependence of energy loss of high momentum partons traversing the dense QCD medium. The dense QCD medium responds to energy loss of high momentum patrons in a pattern consistent with that expected from a hydrodynamic fluid. The hadronization of bulk partonic matter exhibits collectivity with effective partonic degrees of freedom. Nuclear collisions at RHIC provide an intriguing environment, where many constituent quark ingredients are readily available for possible formation of exotic particles through quark coalescence or recombinations.     

Spontaneous P-violation in QCD in extreme conditions

We investigate the possibility of parity being spontaneously violated in QCD at finite baryon density and temperature. QCD is approximated by a generalized σ model with two isomultiplets of scalars and pseudoscalars. The interaction with the chemical potential is introduced via the coupling to constituent quark fields as nucleons are not considered as point-like degrees of freedom in our approach. This mechanism of parity violation is based on interplay between lightest and heavier degrees of freedom and it cannot be understood in simple models retaining the pion and nucleon sectors solely. We argue that, in the appropriate environment (dense and hot nuclear matter of a few normal densities and moderate temperatures), parity violation may be the rule rather than the exception and its occurrence is well compatible with the existence of stable bound state of normal nuclear matter. We prove that the so-called ‘chiral collapse’ never takes place for the parameter region supporting spontaneous parity violation.     

Consistency constraints on from QCD dispersion relations and chiral perturbation theory in decays

We use both old and new theoretical developments in QCD dispersion relation constraints on the scalar form factor in the decay to obtain constraints on the strange quark mass. The perturbative QCD side of the calculation incorporates up to four-loop corrections, while the hadronic side uses a recently developed parameterization constructed explicitly to satisfy the dispersive constraints. Using chiral perturbation theory ( PT) as a model for soon-to-be measured data, we find a series of lower bounds on increasing with the accuracy to which one believes PT to represent the full QCD result.     

Quasipartiele model for the quark-gluon plasma: Equation of state near Tc

We test the quark mass dependence implemented in the quasiparticle dispersion relations of our quasiparticle model for the QCD equation of state by comparing with recently available lattice QCD data employing almost physical quark masses. In addition, we emphasize the capability of our model to successfully describe lattice QCD results (or imaginary chemical potential and to analytically continue the latter to real chemical potential.