Nuclear symmetry energy and proton-rich reactions at intermediate energies

Based on an isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model, effects of high-density behavior of nuclear symmetry energy in the proton-rich reaction Si-22 + Si-22 at a beam energy of 400 MeV/nucleon are studied. It is found that the symmetry energy affects pi(+) production more than pi(-). More interestingly, compared to neutron-rich reactions, for pi(-)/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 Si-22 + Ca-40 to study nuclear symmetry energy is also provided.