Nuclear Physicist Tracks Rare Collided Particles to Better Understand Big Bang

Congratulations are in order for Sooraj Radhakrishnan, Ph.D., a postdoctoral fellow in the Kent State University College of Arts and Sciences’ Department of Physics who performs research in experimental nuclear physics. His data analysis of some rare particles called “charm quarks” that may have existed in the first microsecond of the Big Bang, the emerging point of our universe, was highlighted in a recent issue of the U.S. Department of Energy’s (DOE) Science Bulletin.

Since October 2019, Radhakrishnan has been serving as a research assistant, based at Lawrence Berkeley National Lab in Berkeley, California, under a DOE grant awarded to Declan Keane, Ph.D., and Spyridon Margetis, Ph.D., both professors in the Department of Physics. They along with other personnel in their lab group have played a leading role in the development of the Heavy Flavor Tracker (HFT) detector upgrade installed in the STAR experiment in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab, including software development, project management and physics analysis for the acquired data samples.

In the recent study, the Heavy Flavor Tracker (HFT) detector was used to detect particles such as the three-quark charmed lambda, which decays less than 0.1 millimeter from the center of the particle collisions. The HFT was built to study how “heavy” quarks, i.e., quarks not found in ordinary matter but created in energetic collisions of gold nuclei, interact in hot nuclear matter. Initial studies had shown a major discrepancy between theory and experiment concerning this behavior.

Studying the details of how “light” and “heavy” quarks [like the “charm” quark] combine into doublets and triplets to form semi-stable particles gives us clues about the inner works of the “strong” (nuclear) force, especially in environments where the nuclear matter is “heated” to a few trillion degrees in temperature; conditions that existed in the first microsecond of the Big Bang.

“We used a supervised machine learning technique to suppress the large background for the detection of charmed lambda particles,” Radhakrishnann said. “The analysis was extremely difficult, and the outcome was not guaranteed; it was a long shot, but at the end, we managed to isolate and study these very rare particles in our data samples.”

To learn more about Kent State’s Center for Nuclear Research, visit

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Jim Maxwell, 

Image Caption:
A gold-gold collision recorded by the Heavy Flavor Tracker (HFT) component of the STAR detector at the Relativistic Heavy Ion Collider (RHIC). The white points show "hits" recorded by particles emerging from the collision as they strike sensors in three layers of the HFT. Scientists use the hits to reconstruct charged particle tracks (red and green lines) to measure the relative abundance of certain kinds of particles emerging from the collision – in this case, charmed lambda particles. (Image courtesy of STAR Collaboration)

POSTED: Monday, January 25, 2021 - 5:17pm
UPDATED: Monday, February 8, 2021 - 1:27pm
Jim Maxwell