The Study of Nuclear Physics with Intermediate Energy Probes

University Of South Carolina At Columbia, Columbia SC

Investigators

Abstract

Although ninety-eight percent of the mass of ordinary matter is due to the strong nuclear force, the present theory of that force (Quantum Chromodynamics) is still not fully understood. This award supports the study of the strong nuclear force by probing the substructure of matter. Almost the entire mass of an atom is concentrated in its tiny nucleus, which is made of nucleons that are either positively charged (protons) or electrically neutral (neutrons). These subatomic particles, however, are not elementary but are themselves composite objects made of quarks held together by glue particles (gluons). The structure of nucleons is a manifestation of the strong nuclear force, which is the strongest force known. This research will help advance discovery and understanding in nuclear physics, and promote teaching, training, and learning. The preparation of junior scientists plays a central role in the supported activities. The nuclear physics research program at the University of South Carolina (USC) is mainly based at the Thomas Jefferson National Accelerator Facility in Newport News, Virginia. There, the group uses high-energy electron and photon beams along with sophisticated particle detectors that were developed, in part, at USC as powerful microscopes to study the subatomic world. The group is also preparing the MUSE experiment at the Paul Scherrer Institute in Switzerland. This experiment will address the proton-radius puzzle by scattering muons and electrons off the proton. Through detector development, simulations, management of complex experiments, and data analyses, they will shed light on some of the most profound questions like: What is the structure of the nucleon? What are and how can we excite its internal degrees of freedom? Once excited, in which way does the nucleon decay back to its original state? Does the structure of the nucleon change if it is embedded in dense nuclear matter? The experimental study of these properties gives insight into the nature of the strong force and allows for rigorous tests of the underlying theory.