Nuclear symmetry energy and proton-rich reactions at intermediate energies

Abstract

Based on an isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model, effects of high-density behavior of nuclear symmetry energy in the proton-rich reaction ${}^{22}\mathrm{Si}+{}^{22}\mathrm{Si}$ at a beam energy of 400 MeV/nucleon are studied. It is found that the symmetry energy affects ${\ensuremath{\pi}}^{+}$ production more than ${\ensuremath{\pi}}^{\ensuremath{-}}$. More interestingly, compared to neutron-rich reactions, for ${\ensuremath{\pi}}^{\ensuremath{-}}/{\ensuremath{\pi}}^{+}$ and dense matter's $N/Z$ ratios, effects of symmetry energy in the proton-rich reaction show contrary behaviors. The practical experiment by using the proton-rich reaction ${}^{22}\mathrm{Si}+{}^{40}\mathrm{Ca}$ to study nuclear symmetry energy is also provided.