Observation of an Energy-Dependent Difference in Elliptic Flow between Particles and Antiparticles in Relativistic Heavy Ion Collisions

Abstract

Elliptic flow (v2) values for identified particles at midrapidity in Au+Au collisions, measured by the STAR experiment in the beam energy scan at RHIC at √sNN =7.7–62.4 GeV, are presented. A beam energy-dependent difference of the values of v2 between particles and corresponding antiparticles was observed. The difference increases with decreasing beam energy and is larger for baryons compared to mesons. This implies that, at lower energies, particles and antiparticles are not consistent with the universal number-of-constituent-quark scaling of v2 that was observed at √sNN =200 GeV.