Structure of the Nucleon and Few-Body Nuclear Systems with Electron Scattering

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This award is to support a suite of nuclear physics experiments at the Jefferson National Laboratory (JLab). Electrons from the JLab accelerator will be scattered from light mass nuclear targets, the scattered electrons will then be detected in instruments located in the experimental halls. By measuring the number of scattered electrons at different positions in the detectors, the PIs will be able to compare the experimental results to theoretical models that predict the internal structure of the proton and neutron. Knowing this structure plays a critical role in understanding the strong force, one of the four principal forces that determine the structure of the universe as we know it. The supported investigators will play a major, leading role in all aspects of the project, namely the preparation of all experimental apparatuses to be used, the acquisition of the experimental data, the data analysis, and the publication of the results. The graduate students involved will be exposed to and gain expertise with both hardware and software development. The project is expected to make significant contributions to the advancement of basic nuclear physics science, and to graduate education and training. The project will result in doctoral dissertation topics on related science and instrumentation, which provide the experience needed for careers in education, medical physics, homeland security, technology, and research at national laboratories.The supported research will provide fundamental information on the momentum distributions of the quarks inside the proton and neutron, by using a novel method of directly comparing measurements of inelastic electron scattering from helium-3 (3He) and tritium (3H) nuclei. This method is complementary to that used in past experiments at the Stanford Linear Accelerator Center, which showed the existence of point-like "partons" inside the nucleons, by utilizing inelastic electron scattering from hydrogen and deuterium (2H) nuclei. The new method will eliminate inherent theoretical uncertainties present in the Stanford method. The results will test long-standing predictions of the Quark Model of the nucleon, and of Quantum Chromodynamics, the theory describing the interactions between quarks and gluons. A secondary goal of the award is the improvement and re-submission of a proposal to be submitted to the JLab Proposal Advisory Committee for a measurement of the elastic charge and magnetic form factors of the 3H nucleus, which will provide critical information for the development of a "standard model" describing the structure and dynamics of the simplest, lightest nuclei in nature.