Studies of Pion and Kaon Structure and Validation of the Exclusive Reaction Mechanism

One of the primary goals of twenty-first century physics is the quantitative understanding of the nature of strongly bound subatomic systems in terms of the fundamental structure of matter. Nuclear physics, the subject of this research program at The Catholic University of America, is the study of the atomic nucleus. It is a key scientific field that investigates the properties of matter by performing ground-breaking research to expand our understanding of the sub-atomic world. This program will perform research to advance the knowledge of the underlying quark-gluon structure of the basic building blocks of the atomic nucleus: its protons, neutrons, pions, and kaons. It will contribute to the improvement of sub-atomic particle detectors that are employed in particle accelerators and to educating the future advanced tech work force through training of graduate, undergraduate, and high school students in state-of-the art instrumentation and machine-learning-informed software development. This research program has two primary goals, one to deepen the QCD understanding of pions and kaons - their form factors, their structure functions, and their masses, and the contrast between the structure of these Goldstone bosons and the proton. The second goal of this science program is to provide measurements to validate the framework for 3D (spatial) hadron imaging. The program focuses in the near and intermediate term on Jefferson Lab 12 GeV, and in the long term on the US-based Electron-Ion Collider. The experimental method uses beams of highly-energetic electrons and/or photons to probe deep inside of hadrons by a completely- (or nearly completely-) measured set of only a few particles, through exclusive (and semi-inclusive) scattering processes. The emphasis of the experimentation is on precision measurements of longitudinal-transverse separated deep exclusive meson electroproduction cross sections. Early-career scientists and students at all levels play an integral part in this project, which provides opportunities to gain experience in the design, assembly, and testing of modern subatomic particle detectors, fast signal processing electronics, and scientific data analysis. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.