Probing the density dependence of the symmetry potential in intermediate-energy heavy ion collisions

Based on the ultrarelativistic quantum molecular dynamics model, the effects of the density-dependent symmetry potential for baryons and of the Coulomb potential for produced mesons are investigated for neutron-rich heavy ion collisions at intermediate energies. The calculated results of the Delta(-)/Delta(++) and pi(-)/pi(+) production ratios show a clear beam-energy dependence on the density-dependent symmetry potential, which is stronger for the pi(-)/pi(+) ratio close to the pion production threshold. The Coulomb potential of the mesons changes the transverse momentum distribution of the pi(-)/pi(+) ratio significantly, though it alters only slightly the pi(-) and pi(+) total yields. The pi(-) yields, especially at midrapidity or at low transverse momenta and the pi(-)/pi(+) ratios at low transverse momenta are shown to be sensitive probes of the density-dependent symmetry potential in dense nuclear matter. The effect of the density-dependent symmetry potential on the production of both K-O and K+ mesons is also investigated.