Can the nuclear symmetry potential at supra-saturation densities be negative?

Abstract

In the framework of an isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, for the central $^{197}\mathrm{Au}+^{197}\mathrm{Au}$ reaction at an incident beam energy of $400$ MeV/nucleon, the effect of nuclear symmetry potential at supra-saturation densities on the preequilibrium clusters emission is studied. It is found that for the positive symmetry potential at supra-saturation densities the neutron-to-proton ratio of lighter clusters with mass number $A\ensuremath{\leqslant}3$ [$(n/p){}_{A\ensuremath{\leqslant}3}$] is larger than that of the heavier clusters with mass number $A>3$ [$(n/p){}_{A>3}$], whereas for the negative symmetry potential at supra-saturation densities the $(n/p){}_{A\ensuremath{\leqslant}3}$ is smaller than the $(n/p){}_{A>3}$. This may be considered as a probe of the negative symmetry potential at supra-saturation densities.