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

Abstract Significant differences exist in the elliptic flow v₂ 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 v₂ differences between protons and anti-protons as well as between Λ and $\overline{\Lambda }$ in Au + Au collisions at $\sqrt{s_{\mathrm{NN}}}=7.7$ GeV as a function of the evolution time. It was found that as the evolution time increases, the v₂ differences between protons and anti-protons become more significant than those between Λ and $\overline{\Lambda }$. This phenomenon can be explained by the different constituent quarks of protons and Λ. 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 Δv₂ being larger than Λ Δv₂. 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 v₂ differences between particles and anti-particles.