Hadronic Structure and Dynamics

该项目将对物理强子进行研究，强子是夸克和胶子的可观测复合材料。这些研究与介子和重子两类强子的唯象学有关，也与进一步理解被称为量子色动力学(QCD)的强相互作用基本理论的复杂非微扰域有关。其中一项研究将通过一种称为QCD的1/N展开的理论框架来解决激发重子的现象学问题，其中N是颜色自由度的数量，在自然界中等于3。这项研究的主要目的是描述激发重子的质量、强衰变和光产生过程，其框架与QCD的约束相一致。这一计划与杰斐逊实验室目前的激发重子实验计划有关。我们还将对1/N展开的一些基本方面进行理论研究，特别是对QCD中手征对称性的自发破缺现象进行研究。另一项研究将解决用有效的理论描述低能和中能QCD的问题。特别是，该项目将考虑扩大QCD低能有效理论的有效范围的问题，即手征微扰理论。该计划是制定一种有效的理论，其中低位介子共振被包括在活动自由度中。这一新的有效理论将有助于更准确地描述发生在普通手征微扰理论适用范围之外的过程。总而言之，该项目的目标是用与QCD一致的方法研究强相互作用的物理，主要目的是以这种方式得出具有普遍有效性的严格结果。该项目还有一个重要的教育组成部分，包括培训一名博士生，与博士后同事合作，以及为研究生课程开发基于计算机的教材。

This project will carry out studies in the physics hadrons, which are the observable composites of quarks and gluons. These studies are relevant to the phenomenology of two kinds of hadrons, namely mesons and baryons, as well as to the further understanding of the complex non-perturbative domain of the fundamental theory of strong interactions known as Quantum Chromodynamics (QCD). One of these studies will address the phenomenology of excited baryons by means of a theoretical framework known as the 1/N expansion of QCD, where N is the number of color degrees of freedom, equal to three in nature. The main goal of this study is to describe masses, strong decays and processes of photo-production of excited baryons with a framework that is consistent with the strictures of QCD. This plan is of relevance to the current experimental program on excited baryons at Jefferson Lab. Theoretical studies of some fundamental aspects of the 1/N expansion will also be carried out, especially with focus on the phenomenon of spontaneous breaking of chiral symmetry in QCD. Another study will address the problem of describing QCD at low and intermediate energies with effective theories. In particular, the project will consider the problem of extending the range of validity of the low energy effective theory of QCD known as Chiral Perturbation Theory. The plan is to formulate an effective theory where low-lying meson resonances are included as active degrees of freedom. This new effective theory will help describe with better accuracy processes that take place outside the range of applicability of ordinary Chiral Perturbation Theory. In summary, the objective of the project is in the study of the physics of the strong interactions by means of methods that are consistent with QCD, and the main aim is to arrive in this way at rigorous results that have general validity. The project has also an important education component that includes the training of a PhD student, collaboration with postdoctoral associates, and the development of computer based teaching materials for graduate courses.