Neutron-proton dynamics and pion production in heavy-ion collisions by the AMD+JAM approach

We report the results of the pion production in central collisions of neutron-rich nuclei ¹³²Sn + ¹²⁴Sn at 300 MeV/nucleon using an approach that combines antisymmetrized molecular dynamics (AMD) and a hadronic cascade model (JAM). The dynamics of neutrons and protons is solved by AMD, and then pions and Δ resonances in the reaction process are handled by JAM. We show quantitatively that the Δ production ratio is almost identical to the neutron-to-proton squared ratio (N/Z)² in the high-density and high-momentum region, and it is directly reflected in the π^-/π⁺ ratio, with some modification in the final stage of the reaction. We also discuss that Pauli blocking plays some important role on the pion observables. (author)