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Leah Broussard: Chasing big physics problems

Leah Broussard. Image credit: Carlos Jones, ORNL

In 2019, nine ORNL early career researchers were recognized with prestigious awards from the White House and the Department of Energy—the Presidential Early Career Award for Scientists and Engineers, or PECASE, and the DOE Early Career Research Program Award. We sat down with these promising young scientists to talk about their backgrounds and current research.

Leah Broussard has always embraced challenges.

“I like to chase problems,” she said. “I go wherever I find the most fun.”

Chasing problems is what first led her to physics in her early teens, when someone told Broussard that was the hardest thing she could do. It also inspired her Early Career Award-winning proposal, “Systematics of precision neutron physics experiments.” 

The research will push boundaries in precision by characterizing systematic uncertainties—tricky data errors that arise from inaccuracies in measurement or observation—for two of the world’s most ambitious physics experiments, both being conducted at ORNL’s Spallation Neutron Source. These are a neutron beta-decay experiment called the “Neutron ‘a’ ‘b’”—or Nab—and the upcoming neutron Electric Dipole Moment, or nEDM, experiment. 

The Nab uses neutron decay to explore the weak interaction between quarks—tiny particles that make up protons and neutrons. It will test the Standard Model, which encompasses our understanding of three of the four fundamental forces (the strong and weak forces and electromagnetism).

The nEDM experiment studies neutrons for a small separation of charge called the electric dipole moment. If a large enough EDM is found, it would indicate missing physics in the Standard Model that could explain why the universe contains matter but almost no antimatter, Broussard said. Such findings would help inform a new model—one that solves these unanswered physics questions.

Broussard will seek to improve Nab’s precision by measuring timing inaccuracies in the detection of protons and electrons produced during neutron decay. For the nEDM, she’ll create more realistic models of the experiment using ORNL’s Summit supercomputer to reduce uncertainties caused by false signs of an electric dipole moment. 

A project incorporating both Summit and SNS is perfect for Broussard, who triple-majored in math, physics and computer science at Tulane University. She earned a doctorate in physics from Duke and spent three years at Los Alamos National Laboratory before accepting a Wigner Fellowship at ORNL in 2016.

She chose ORNL specifically for the kind of high-level neutron work she’s doing now.

“This work can tell us something fundamental about our universe,” Broussard said.—Abby Bower