Continuum QCD Modeling of Hadron Properties

对质子、中子和其他强相互作用的亚原子粒子的内部结构的完整理解仍然是难以捉摸的。虽然量子色动力学（QCD），粒子物理学标准模型的相关部分，是一个既定的理论框架，它是非常困难的计算延伸到大距离的现象，如质子的大小。格子QCD是一种数值第一性原理技术，它严重依赖于高性能的计算资源，只能精确计算质子和中子等粒子的某些性质。对于其他性质，研究人员依赖于物理上动机良好的现象学模型。在这个更广泛的背景下，研究者和他的学生将开发和应用改进的QCD模型来研究亚原子粒子中组分夸克和胶子的分布，如π介子，K介子和质子。这些努力为杰斐逊国家加速器设施正在进行的实验工作提供了理论支持。参与这项研究的研究生将接受理论核物理方面的培训，并将有机会在核科学的前沿研究问题，从而接受培训，为他们进入核科学竞技场急需的劳动力做好准备。在QCD中建立非微扰模型的Dyson-Schwinger方程方法保留了QCD的短程重整化群行为，而在红外域中的建模则由经验方法指导，该方法保留了已知产生宇宙中至少98%可见稳定物质质量的动力学手征对称性破缺。这种方法是检查对已建立的结果格QCD，并用于扩展和补充格QCD的域格结果是目前不可用。这项工作将分析和解释有关亚原子粒子的夸克和胶子结构以及弹性和跃迁形状因子的实验结果。本计画亦将发展一种改良的实用方法，以求解激发态介子的QCD束缚态方程，并将探讨最近提出的一种近似方法的局限性，以计算格点QCD的部分子分布。

A complete understanding of the internal structure of protons, neutrons and other strongly interacting subatomic particles remains elusive. Although Quantum Chromodynamics (QCD), the relevant part of the Standard Model of particle physics, is an established theoretical framework, it is extremely difficult to perform calculations for phenomena that extend over large distances such as the size of the proton. Lattice-QCD, a numerical first-principles technique that relies heavily on high-performance computational resources, is able to calculate accurately only certain properties of particles such as protons and neutrons. For other properties, researchers rely on physically well-motived phenomenological models. In this broader context, the investigator and his students will develop and apply improved QCD models to study the distribution of constituent quarks and gluons in subatomic particles, such as pions, kaons, and protons. These efforts provide theoretical support to ongoing experimental efforts at the Jefferson National Accelerator Facility. Graduate students involved in this research will be trained in theoretical nuclear physics and will have the opportunity to work on research problems at the forefront of nuclear science, thereby receiving training that prepares them for entering the much-needed workforce in the nuclear science arena. The Dyson-Schwinger equations approach to nonperturbative model building in QCD preserves the short distance renormalization group behavior of QCD, while modeling in the infrared domain is guided by an empirical approach that preserves the dynamical chiral symmetry breaking known to generate at least 98% of the mass of visible stable matter in the universe. This approach is checked against established results of Lattice-QCD and is used to extend and complement Lattice-QCD for domains where lattice results are not presently available. This work will analyze and interpret experimental results about the quark and gluon structure of sub-atomic particles and elastic and transition form factors. This project will also develop an improved practical method for solving the QCD bound state equation for excited state mesons and will explore the limitations of a recently proposed approximate approach to parton distributions for Lattice-QCD.