Hadronic and Nuclear Structure and Dynamics

Hampton University, Hampton VA

Investigators

Abstract

The understanding of the strong interactions, the force that determines the structure of atomic nuclei, is one of the most challenging problems in the Standard Model of particle physics, which describes the number and properties of all the elementary particles. The fundamental theory of the strong interactions, based on the theory of quarks and gluons known as Quantum Chromodynamics (QCD), has a very complex dynamics which gives rise to the rich properties of hadrons (baryons, including protons and neutrons, and mesons and their excitations) and also to the complexity observed in nuclear interactions and structure. The challenges are therefore many and very complex. Those challenges require a variety of experimental efforts, as well as theoretical efforts. In this context, this project will further develop the connection between the fundamental theory of QCD and hadronic/nuclear physics. It is expected that tools and methods developed in that context may have a broader domain of applications. The PI is a joint appointee in the Theory Group at Jefferson Lab, providing him with the opportunity to focus on Jefferson Lab related physics. An important mission of the project is the education and training at Hampton University of graduate and undergraduate students. An additional broader impact of the project will be the PI's interaction with scientists involved in Jefferson Lab experiments. This project focuses on low and intermediate energy strong interactions in single hadron and few nucleon problems, as well as some fundamental aspects of QCD. The methods used are based in rigorous descriptions of the strong interactions known as effective theories, which are consistent with QCD, and make use of experimental as well as lattice QCD calculations results. The aim is to advance the theoretical knowledge of QCD and the develop theoretical methods. More specifically, in single hadrons, two main lines of research will be pursued: 1) Development and applications of an improved chiral effective theory in baryons, where the combination of the low energy and the 1/Nc expansions (Nc is the number of color degrees of freedom in QCD) is implemented; applications to baryon observables, and in particular to results obtained in Lattice QCD for those observables will be pursued, where in particular the quark mass dependencies accessible through Lattice QCD will be utilized for analyzing issues of convergence of the effective theory. Particular emphasis will be on the applications to baryons involving strangeness, where there are still unresolved issues with the implementation of effective theories due to the relatively large mass of the strange quark. In particular, these studies have impact in for improving the accuracy of the extraction of weak interaction parameters from hyperon decays. 2) Study of excited baryons in the framework of the 1/Nc expansion, which has as main aim the use of that fundamental expansion of QCD to organize the description of baryon resonances; this work has an impact in the analysis of current experimental results on baryon resonances from various facilities, in particular Jefferson Lab, and it can also be applied to the current Lattice QCD calculations of the excited baryon spectrum. In few body physics, the research is focused on applying the combined chiral effective theory and 1/Nc expansion to study the nucleon-nucleon interaction. Among the fundamental aspects of QCD, the project will focus on pure glue-dynamics, studying its fundamental non-perturbative quantities, namely gluon condensate and topological susceptibility using methods of holographic QCD.