Probing high-density behavior of symmetry energy from pion emission in heavy-ion collisions

Abstract

Within the framework of the improved isospin dependent quantum molecular dynamics (ImIQMD) model, the pion emission in heavy-ion collisions in the region 1 A GeV is investigated systematically, in which the pion is considered to be mainly produced by the decay of resonances $\triangle$(1232) and N*(1440). Total pion multiplicity and $\pi^{-}/\pi^{+}$ yields are calculated for the reaction $^{197}$Au+$^{197}$Au in central collisions for selected Skyrme parameters SkP, SLy6, Ska and SIII, which correspond to different modulus of incompressibility of symmetric nuclear matter and different stiffness of the symmetry energy, and also compared them with the measured data by the FOPI collaboration. The excitation function of the neutron/proton ratio of free nucleons and the ratio of the charged pions ($\pi^{+}$ and $\pi^{-}$) per nucleon produced in heavy $^{197}$Au+$^{197}$Au over light $^{40}$Ca+$^{40}$Ca reactions are also investigated systematically.