The elliptic flow difference between baryons and anti-baryons in heavy collision with SMASH Model

A significant difference in the elliptic flow v₂ for particles and their corresponding antiparticles, which is more pronounced for baryons and anti-baryons, was observed in the STAR experiment during the Beam Energy Scan I (BES-I) at RHIC. By employing the SMASH model, we study the v₂ difference between protons and anti-protons, as well as between Λ and Λ, in Au + Au collisions at √s_NN = 7.7 GeV as a function of evolution time. It finds that as the evolution time increases, the v₂ difference between protons and anti-protons becomes more pronounced compared to that between Λ and Λ. This phenomenon can be explained by the different constituent quarks of protons and Λ. Since some of the u quarks and d quarks come from the colliding nuclei and are transported to mid-rapidity, they undergo more interactions than produced quarks, resulting in the proton △v₂ being larger than the Λ △v₂. We compare the SMASH calculations with STAR BES-I data and argue that higher precision data from BES-II will provide constraints on theoretical frameworks to interpret the v₂ differences of particles and anti-particles.