Continuum QCD Modeling of Hadron Properties

Kent State University, Kent OH

Investigators

Abstract

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.