Influence of the treatment of initialization and mean-field potential on the neutron to proton yield ratios

In this work, we first investigate how to reproduce and how well one can reproduce the Woods-Saxon density distribution of initial nuclei in the framework of the improved quantum molecular dynamics model. Then, we propose a new treatment for the initialization of nuclei which is correlated with the nucleonic mean-field potential by using the same potential energy density functional. In the mean field potential, the three-body force term is accurately calculated. Based on the new version of the model, the influences of precise calculations of the three-body force term, the slope of symmetry energy, the neutron-proton effective mass splitting, and the width of the wave packet on heavy ion collision observables, such as the neutron to proton yield ratios for emitted free nucleons [R(n/p)] and for coalescence invariant nucleons [R-ci (n/p)] for Sn-124+ Sn-112 at the beam energy of 200 MeV per nucleon, are discussed. Our calculations show that the spectra of neutron to proton yield ratios [R(n/p)] can be used to probe the slope of symmetry energy (L) and the neutron-proton effective mass splitting. In detail, the R(n/p) in the low kinetic energy region can be used to probe the slope of symmetry energy (L). With a given L, the inclination of R(n/p) to kinetic energy (E-k) can be used to probe the effective mass splitting. In the case where the neutron-proton effective mass splitting is fixed, R(n/p) at high kinetic energy can also be used to learn the symmetry energy at suprasaturation density.