Mean-field potential effects on particle and antiparticle elliptic flows in the beam-energy scan program at RHIC

The elliptic flow splitting between particles and their antiparticles has recently been observed by the STAR Collaboration in the beam-energy scan program at the Relativistic Heavy Ion Collider. In studies based on transport models, we have found that this splitting can be explained by the different mean-field potentials acting on particles and their antiparticles in the produced baryon-rich matter. In particular, we have shown that the experimentally measured relative elliptic flow difference can help constrain the vector coupling constant in the Nambu-Jona-Lasinio model used in describing the partonic stage of heavy-ion collisions. This information is useful for locating the critical point in the QCD phase diagram and thus understanding the phase structure of QCD.