Elliptic Flow Differences between Baryons and Anti-Baryons in Heavy-Ion Collisions Using SMASH Model

Significant differences exist in the elliptic flow v_2 for particles and their corresponding anti-particles. These differences, which are more significant for baryons and anti-baryons, were observed from the solenoidal tracker (STAR) experiment during Beam Energy Scan I (BES-I) at relativistic heavy ion collider (RHIC). By employing the simulated many-accelerated strongly interacting hadrons (SMASH) model, we studied the v_2 differences between protons and anti-protons as well as between \varLambda and \bar\varLambda in Au + Au collisions at \sqrts_\rm NN=7.7 GeV as a function of the evolution time. It was found that as the evolution time increases, the v_2 differences between protons and anti-protons become more significant than those between \varLambda and \bar\varLambda. This phenomenon can be explained by the different constituent quarks of protons and \varLambda. Given that some of the u and d quarks come from the colliding nuclei and are transported to midrapidity, they undergo more interactions than the produced quarks, resulting in protons \Delta v_2 being larger than \varLambda \Delta v_2. We compared the SMASH calculations with STAR BES-I data and concluded that higher-precision data from BES-II will set constraints on theoretical frameworks to interpret the v_2 differences between particles and anti-particles.