Probing nuclear symmetry energy with the sub-threshold pion production

Abstract

Within the framework of semiclassical Boltzmann-Uehling-Uhlenbeck (BUU) transport model, we investigated the effects of symmetry energy on the sub-threshold pion using the isospin MDI interaction with the stiff and soft symmetry energies in the central collision of ${}^{48}$Ca + ${}^{48}$Ca at the incident beam energies of 100, 150, 200, 250 and 300 MeV/nucleon, respectively. We find that the ratio of ${\pi }^{-}/{\pi }^{+}$ of sub-threshold charged pion production is greatly sensitive to the symmetry energy, particularly around 100 MeV/nucleon energies. Large sensitivity of sub-threshold charged pion production to nuclear symmetry energy may reduce uncertainties of probing nuclear symmetry energy via heavy-ion collision.

Comments: 5 pages, 5 figures, typo corrections, submitted to Chinese Physics Letters