Effects of pion potential and nuclear symmetry energy on the $π^{-}/π^{+}$ ratio in heavy-ion collisions at beam energies around the pion production threshold

Wen-Mei Guo, Gao-Chan Yong, Hang Liu, Wei Zuo

Published 2014-10-18Version 1

Within the framework of an isospin-dependent Boltzmann-Uehling-Uhlenbeck(IBUU) transport model, we studied the effects of the pion potential and the symmetry energy on the pion production in the central $^{197}Au+^{197}Au$ collisions around the pion production threshold. It is found that the pion potential affects the value of $\pi^-/\pi^+$ ratio around the Coulomb peak and also in the high energy region of pion mesons. The effect of the pion potential on the $\pi^-/\pi^+$ ratio becomes large in heavy-ion collisions at beam energies below the pion production threshold. And at beam energies below the pion production threshold, with the pion potential, the effect of the symmetry energy on the $\pi^-/\pi^+$ ratio becomes quite small compared with that above the pion production threshold.