Theoretical Nuclear Physics

量子色动力学（QCD）是强相互作用的理论，夸克在胶子力的约束下形成质子和其他核物理中的重子，以及夸克-反夸克粒子介子。胶子也有可能形成没有夸克成分的粒子，称为胶球。胶球的发现和研究是核/粒子物理最重要的领域之一。利用QCD，我们正在研究介子和胶球的可能状态，重点是确定实验来测试我们的理论图景。特别重要的是我们最近对一个低质量胶球的预测，我们认为它与一个叫做Sigma的双介子共振强烈耦合。我们正在研究粒子的衰变速率，这将为胶球/ σ理论提供检验。有可能在杰斐逊实验室进行其中一些实验测试。我们还在进行波美龙的研究，人们早就知道波美龙的交换在高能弹性和衍射过程中起主导作用。几乎可以肯定的是，Pomeron主要由胶水组成，最近我们的团队给出了强有力的证据，证明Pomeron与胶球（glueball）密切相关，包括我们提出的glueball/sigma。我们将计算西格玛生产的横截面，以测试波美龙的性质。实验可以在洛斯阿拉莫斯实验室和日本提议的50个GeV加速器上进行。使用布鲁克海文实验室RHIC设备的质子-质子对撞机将非常适合横截面的实验测量。有限密度和有限温度下强子的性质也在研究中。我们已经完成了在低于手性相变温度下的强子物质的初步研究，手性相变发生在所谓的大爆炸后大约百万分之一秒的宇宙温度下。我们将研究瞬子，某些胶子模式，对低于和高于这一相变的物质性质的影响，并提出在RHIC加速器上进行测试。我们还将在宇宙微波背景的观测研究中研究这种早期宇宙相变的可能证据。这些关于核/粒子物理和宇宙学之间关系的跨学科研究使用了凝聚态物理研究中发展起来的场论方法。

Quantum Chromodynamics (QCD) is the theory of strong interactons, with quarks confined by gluonic forces to form protons and other baryons of nuclear physics, as well as quark-antiquark particles, the mesons. It is also possible for the gluons to form particles, called glueballs, without quark constituents. The discovery and study of glueballs is one of the most important areas of nuclear/particle physics. Using QCD, we are investigating possible states of mesons and glueballs with emphasis on identifying experiments to test our theoretical picture. Of particular importance is our recent prediction of a low-mass glueball which we feel is strongly coupled to a two-pion resonance, called the Sigma. We are investigating decay rates of particles which will provide tests of this theory of the glueball/sigma. It is possible to carry out some of these experimental tests at Jefferson Laboratory. We are also carrying out investigations of the Pomeron, whose exchange has long been known to dominate high energy elastic and diffractive processes. It is almost certain that the Pomeron is composed largely of glue, and recently our group has given strong evidence that the Pomeron is closely related to glueballs, including our proposed glueball/sigma. We shall calculate cross sections for sigma production to test the nature of the Pomeron. Experiments could be carried out at the 50 GeV accelerators proposed at Los Alamos Laboratory and in Japan. The proton-proton collider, using the RHIC facility at Brookhaven Laboratory, would be excellent for experimental measurements of the cross sections. Properties of hadrons at finite densities and temperatures are also being investigated. We have completed a preliminary study for hadronic matter at temperatures below the chiral phase transition, which occurs at the temperature of the universe about a millionth of a second after the so-called big bang. We shall study the effect of instantons, certain gluonic modes, on the properties of matter both below and above this phase transition, and propose tests at the RHIC accelarator. We shall also investigate possible evidence for this early-universe phase transition in observational studies of the cosmic microwave background. These interdisciplinary investigations of relationships between nuclear/particle physics and cosmology use field theoretic methods developed in studies of condensed matter physics.