Probing the nuclear symmetry energy using single and doubleπ−/π+ratios from mirror reaction systems

Abstract

Within the framework of an isospin and momentum-dependent hadronic transport model, the single and double ${\ensuremath{\pi}}^{\ensuremath{-}}/{\ensuremath{\pi}}^{+}$ ratios in mirror reaction systems of ${}^{22}\mathrm{O}+{}^{22}\mathrm{Na}$ and ${}^{22}\mathrm{Si}+{}^{22}\mathrm{Na}$ at the incident beam energy of 400 MeV/nucleon are studied. It is found there are opposite symmetry energy effects on the single ratios from the neutron-rich and the proton-rich reactions. Due to the opposite isospin degrees of freedom, the double ${\ensuremath{\pi}}^{\ensuremath{-}}/{\ensuremath{\pi}}^{+}$ ratio taken from neutron-rich and proton-rich reactions displays more sensitivity to the density dependence of the nuclear symmetry energy in broader pion kinetic energy region; thus the double charged pion ratio from the mirror systems may be a useful probe for the high-density behavior of the nuclear symmetry energy.