Kumar Receives DOE Support for Weak Force Studies of Electrons and Heavy Nuclei

Krishna Kumar
Krishna Kumar

Krishna Kumar, the Robert L. Gluckstern Professor in Physics, recently received a three-year, $1.1 million grant from the U.S. Department of Energy (DOE) to support the launch a suite of new experiments at DOE’s Thomas Jefferson National Accelerator Facility in Newport News, Virginia, to measure radii of neutron distributions in heavy nuclei.

The grant will also support analysis and publication of earlier research in medium-energy nuclear physics by the Kumar lab. Data collected with this apparatus from 2019 and 2020 will provide precise new measurements of the extent to which neutrons distend, or bulge beyond protons in heavy nuclei. This should add “important new constraints on the density dependence of the symmetry energy of neutron matter and leading to a better understanding of neutron forces and neutron stars,” DOE says.

Measurements by the Kumar lab’s new experiments will help to precisely map out the charge and magnetization distributions of “up” and “down” quarks inside the proton, as well, Kumar says.“Our team can now launch into the exciting new projects that have been envisioned and planned for the next few years. It provides a tremendous opportunity for new graduate and undergraduate students at UMass to engage in exciting fundamental physics research,” he points out.

Kumar and colleagues will also lead in the design of a new apparatus for use in a dedicated six-year experimental project at the Virginia facility.It will use electron beams to bombard hydrogen atoms “specifically to understand and measure the weak force between two electrons,” Kumar explains. “This will make a really precise measurement of that, which will have implications for our understanding of the early universe.”

Kumar is now beginning his second year of the seven-year term as Gluckstern Professor since he rejoined the physics department after a stint in the experimental nuclear physics program at Stony Brook University in 2014-18.

Kumar says his experimental nuclear physics research has strong connections to particle physics, with the goal ofunderstanding “the inner workings deep inside the atom, how matter is put together, what are the most fundamental constituents of matter as you get to smaller and smaller scales, and whether we understand how the forces work at those scales.”

“That leads you immediately to understanding the early universe in the instants after the Big Bang. We try to understand how the universe evolved from that very tiny size through various epochs to the formation of galaxies, our solar system and so on. Physics, astrophysics and astronomy all work coherently to try to put the picture together.”