Medium effects on pion production in heavy ion collisions
Zhen Zhang🇺🇸 · Che Ming Ko🇺🇸
Within the framework of the relativistic Vlasov-Uehling-Uhlenbeck transport model based on the relativistic nonlinear NL interaction, we study pion in-medium effects on the ratio in Au+Au collisions at the energy of . These effects include the isospin-dependent pion s-wave and p-wave potentials, which are taken from calculations based on the chiral perturbation theory and the -hole model, respectively. We find that the ratio in this collision is suppressed by the pion s-wave potential but enhanced by the p-wave potential, with a net effect of a significantly suppressed ratio. Including also the in-medium threshold effects on resonance production and decay and using a nuclear symmetry energy with a slope parameter by reducing the coupling of isovector-vector meson to nucleon, our result is in good agreement with measured ratio from the FOPI Collaboration. We further investigate the pion in-medium effects on the ratio of charged pions as a function of their kinetic energies.