Researchers from Stony Brook University are among a group of nuclear physicists analyzing data from the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC) — a U.S. Department of Energy (DOE) Office of Science user facility for nuclear physics research at Brookhaven National Laboratory. Results of their work have been published in the journal Nature Physics and provide additional evidence that collisions of miniscule projectiles with gold nuclei create tiny specks of the perfect fluid that filled the early universe.
Scientists are studying this hot soup made up of quarks and gluons — the building blocks of protons and neutrons — to learn about the fundamental force that holds these particles together in the visible matter that makes up our world today. The ability to create such tiny specks of the primordial soup (known as quark-gluon plasma) was initially unexpected and could offer insight into the essential properties of this remarkable form of matter.
“This work is the culmination of a series of experiments designed to engineer the shape of the quark-gluon plasma droplets,” said PHENIX collaborator Jamie Nagle, University of Colorado, Boulder, who helped devise the experimental plan as well as the theoretical simulations the team would use to test their results.
Stony Brook scientists from the Center for Frontiers in Nuclear Science (CFNS) in the Department of Physics and Astronomy within the College of Arts and Sciences have contributed key measurements to these results. Senior Postdoctoral Researcher Carlos E. Perez Lara, working with Distinguished Teaching Professor Thomas Hemmick and Professor Axel Drees, calibrated and analyzed data collected during 2016 by the MPC-EX preshower detector that was used for systematics studies in the d+Au collision system. Perez Lara gained experience measuring flow in heavy ion collisions when he was principal researcher of the first measurements of open charm and strange flow at large systems in the ALICE experiment at CERN before coming to Stony Brook.
“Many measurements have been presented on these phenomena in recent years by both the Large Hadron Collider and RHIC, but only now we can demonstrate a strong connection between the flow amplitude and the initial system geometry,” said Perez Lara. “These results bring new exciting arguments that support the formation of quark-gluon plasma at such small scales.”
The MPC-EX preshower detector was assembled at Stony Brook by a team led by Professor Hemmick with substantial contributions from multiple undergraduate researchers. The detector was installed into the PHENIX experiment in 2015.
The PHENIX collaboration’s latest paper includes a comprehensive analysis of collisions between small projectiles (single protons, two-particle deuterons, and three-particle helium-3 nuclei) with large gold nuclei “targets” moving in the opposite direction at nearly the speed of light. The team tracked particles emerging from these collisions, looking for evidence that their flow patterns matched up with the original geometries of the projectiles, as would be expected if the tiny projectiles were indeed creating a perfect liquid quark-gluon plasma.
“RHIC is the only accelerator in the world where we can perform such a tightly controlled experiment, colliding particles made of one, two, and three components with the same larger nucleus, gold, all at the same energy,” said Nagle.
This work was supported by the DOE Office of Science, and by all the agencies and organizations supporting research at PHENIX.