Suffolk Reporter

Nuclear physics theorists at the U.S. Department of Energy's Brookhaven National Laboratory have successfully used supercomputers to predict the distribution of electric charges in mesons. These particles, composed of a quark and an antiquark, are part of a broader class known as hadrons. Researchers aim to explore these particles further through high-energy experiments at the upcoming Electron-Ion Collider (EIC) being constructed at Brookhaven Lab.

"The fundamental science goal of the EIC is to understand how the properties of hadrons, including mesons and more familiar protons and neutrons, arise from the distributions of their constituent quarks and gluons," stated Swagato Mukherjee, a theorist at Brookhaven Lab who led this research. The study focuses on understanding how quarks and gluons contribute to the mass and structure of visible matter.

Recent predictions published in Physical Review Letters align with measurements from low-energy experiments conducted at DOE's Thomas Jefferson National Accelerator Facility. These findings extend into the high-energy domain anticipated for future EIC experiments, expected to begin in the early 2030s.

Beyond establishing expectations for EIC measurements, researchers utilized their predictions alongside independent supercomputer calculations to validate an approach called factorization. This method breaks down complex physical processes into two components or factors. The validation will enable further EIC predictions and interpretations of experimental results.

The EIC will collide high-energy electrons with protons or atomic nuclei to examine hadrons' inner structures. Scientists use factorization to convert precise measurements into detailed images of matter's building blocks within hadrons. "But does this actually work — separating one phenomenon into these two factors?" asked Qi Shi, a visiting graduate student in Brookhaven Lab’s Nuclear Theory Group.

To confirm this approach, scientists reversed the factorization process. They used supercomputers and space-time lattice simulations to calculate quark-antiquark distributions in mesons while employing simpler calculations for quark/gluon interactions with photons. Comparing these new predictions with previous ones validated that factorization is a viable method for solving such problems.

"In this case, we can fully compute everything using the lattice," said Shi. "We chose this specific case because we can calculate both the left- and right-hand sides of the equation using independent calculations to show that factorization works."

Peter Petreczky, group leader and co-author of the paper, emphasized that "this work shows that the factorization approach works." The research was supported by various DOE facilities and collaborations.