Effects of density-dependent scenarios of in-medium nucleon-nucleon interactions in heavy-ion collisions

Using a more reasonable separate density-dependent scenario instead of the total density-dependent scenario for in-medium nn, pp, and np interactions, we examine effects of differences of in-medium nucleon-nucleon interactions in two density-dependent scenarios on isospin-sensitive observables in central Au-197 + Au-197 collisions at 400 MeV/nucleon. It is shown that the symmetry potentials and resulting symmetry energies in two density-dependent scenarios indeed begin to deviate at nonsaturation densities, especially at suprasaturation densities. Naturally, several typical isospin-sensitive observables such as the free neutron-proton ratios and the pi(-)/pi(+) ratios in heavy-ion collisions are affected significantly. Moreover, to more physically detect the differences between the nucleon-nucleon interactions in two density-dependent scenarios, we also map the nucleon-nucleon interaction in the separate density-dependent scenario into that in the total density-dependent scenario through fitting the identical constraints for symmetric nuclear matter as well as the identical slope parameter of nuclear symmetry energy at the saturation density. It is shown that two density-dependent scenarios also lead to essentially different symmetry potentials especially at high densities although they can lead to the identical equation of state for the symmetry nuclear matter as well as the identical symmetry energy for the isospin asymmetric nuclear matter. Consequently, these isospin-sensitive observables are also appreciably affected by the different density-dependent scenarios of in-medium nucleon-nucleon interactions. Therefore, according to these findings, it is suggested that effects of the separate density-dependent scenario of in-medium nucleon-nucleon interactions should be taken into account when probing the high-density symmetry energy using these isospin-sensitive observables in heavy-ion collisions.