Physicists track sequential ‘melting’ of upsilons

Scientists using the Relativistic Heavy Ion Collider (RHIC) to study some of the hottest matter ever created in a laboratory have published their first data showing how three distinct variations of particles called upsilons sequentially “melt,” or dissociate, in the hot goo. The results, just published in Physical Review Letters, come from RHIC’s STAR detector, one of two large particle tracking experiments at this U.S. Department of Energy (DOE) Office of Science user facility for nuclear physics research.