NSF-BSF: Precision Muon and Electron Scattering to Probe Low-Energy Proton Structure

This award provides funding for the NSF-supported research activities of the PI and his group at Hampton University, a Historically Black College and University (HBCU) in Virginia, USA. The group will work on the Muon Scattering Experiment (MUSE) at the Paul-Scherrer Institute in Switzerland. The MUSE experiment is an investigation into the so-called “proton radius puzzle”.

The size of the proton is a fundamental quantity with considerable uncertainty due to conflicting measurements and methods. The MUSE experiment will measure the proton charge radius with high precision via the elastic scattering of electrons and muons off protons. The experiment will provide data to constrain the possible explanations of the puzzle and has the potential to reveal new physics beyond the Standard Model.

The project offers opportunities for students and postdocs at a minority serving institution to participate in forefront international research.

The MUSE experiment aims to address one of the most pressing questions in nuclear and particle science to date; to measure the radius of the proton. MUSE will use mixed muon and electron beams of either charge (μ+/e+, μ−/e−) to make precise measurements of the lepton-proton elastic scattering cross sections, over a broad kinematic range, with the goal to extract the proton charge radius for each probe.

The experiment will determine, with high precision, if there is any difference seen for the proton charge radius observed by electron versus muon scattering. At the same time, it will provide tight constraints on nuclear theory. The PI is one of the original initiators of the MUSE project.

The coPI is a junior faculty member whose PhD work focused on similar measurements. The group will play a major role in running the experiment and analyzing the data. Notably, the group is responsible for high-resolution beam particle tracking at MUSE using GEM detectors.

Broader Impact: the PI’s research program provides new research and educational opportunities for students from minority populations, predominantly African-Americans, and postdoctoral researchers. Hampton University is the only HBCU in the US offering a PhD program in Nuclear Physics. This project combines state-of-the-art detector development at Hampton University with forefront research at facilities around the globe, such as PSI and Jefferson Lab.

The PI has successfully worked with Hampton University undergraduate and graduate students for many years, and he has been a dedicated mentor for postdoctoral researchers and a strong supporter of women in science. Further, the PI has maintained strong partnerships with other institutions, with the clear goal of attracting graduate students to the physics PhD and Master programs at Hampton University and providing a pipeline of talented undergraduate students toward graduate education in top schools, to ultimately increase the number of African-American PhDs.

The development and operation of GEM detectors for MUSE constitutes a strong basis to advance this novel technology with potential future applications in other experiments, as well as in the medical sector and national security.

The project is co-funded by the Physics Division, and the Historically Black Colleges and Universities Undergraduate Program. This award also provides Binational Science Foundation (BSF) funding for the group at The Hebrew University of Jerusalem, Israel.

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.