Suffolk Reporter

Stony Brook University researchers have developed a novel approach to examine atomic nuclei shapes using high-energy particle collisions at the Relativistic Heavy Ion Collider (RHIC) located at Brookhaven National Laboratory (BNL). This new method, detailed in a paper published in Nature, complements existing lower energy techniques for studying nuclear structure and enhances scientists' understanding of the nuclei that constitute most visible matter.

"In this new measurement, we not only quantify the overall shape of the nucleus — whether it’s elongated like a football or squashed down like a tangerine — but also the subtle triaxiality, the relative differences among its three principal axes that characterize a shape in between the ‘football’ and ‘tangerine,’” explained Jiangyong Jia. Jia is a professor in Stony Brook's Department of Chemistry and an adjunct professor in the Department of Physics and Astronomy. He holds a joint appointment at BNL and is one of the principal authors on the STAR Collaboration publication.

Understanding nuclear shapes has implications for various physics questions, such as predicting which atoms are likely to undergo nuclear fission, understanding how heavy atomic elements form during neutron star collisions, and identifying nuclei that could lead to discoveries about exotic particle decay.

The enhanced knowledge of nuclear shapes will enrich scientists' comprehension of initial conditions similar to those present shortly after the universe's formation. These conditions are recreated during RHIC's energetic particle collisions. The technique can be applied to further analyze data from RHIC as well as from nuclear collisions at Europe's Large Hadron Collider (LHC). It will also be relevant for future investigations at the Electron-Ion Collider, currently being designed at BNL. RHIC serves as a U.S. Department of Energy Office of Science user facility dedicated to nuclear physics research.

Jia emphasized, "The best way to demonstrate the robustness of nuclear physics knowledge gained at RHIC is to show that we can apply the technology and physics insights to other fields. Now that we’ve demonstrated a robust way to image nuclear structure, there will be many applications."

To validate their method, STAR scientists examined particle flow and momentum post-collision and compared these with hydrodynamic expansion models for different quark-gluon plasma shapes. They assessed central collisions involving gold nuclei—considered nearly spherical based on low energy studies—and uranium nuclei with an elongated football-like shape. Given gold nuclei's near-spherical nature, minimal variation was expected in emitted particles' flow patterns across different collisions.

For more details, visit BNL's website.