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 Δ-/Δ++ and π-/π+ production ratios show a clear beam-energy dependence on the density-dependent symmetry potential, which is stronger for the π-/π+ ratio close to the pion production threshold. The Coulomb potential of the mesons changes the transverse momentum distribution of the π-/π+ ratio significantly, though it alters only slightly the π- and π+ total yields. The π- yields, especially at midrapidity or at low transverse momenta and the π-/π+ 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 K0 and K+ mesons is also investigated