Correlation of the symmetry energy at subsaturation densities and neutron-skin thickness in low-energy antiproton induced reactions

Abstract

Within the framework of Lanzhou quantum molecular dynamics transport model, the neutron-skin thickness and its impact on the nuclear dynamics induced by low-energy antiprotons are investigated thoroughly. The correlation of the neutron-skin thickness and stiffness of symmetry energy is implemented into the transport model via the Fermi distributions of the proton and neutron density profiles. It is found that antiprotons are predominantly annihilated in the subsaturation density region (0.4$\rho_{0}$-0.8$\rho_{0}$). The isospin ratios of free neutrons to protons (n/p) and charged pion yields ($\pi^{-}$/$\pi^{+}$) in collisions of antiprotons on $^{48}\rm{Ca}$ and $^{208}\rm{Pb}$ are analyzed systematically for extracting the symmetry energy in the domain of subsaturation densities. The n/p ratio is sensitive to the stiffness of symmetry energy in the low-density region and a soft symmetry energy leads to the larger n/p ratio, in particular with decreasing the beam momentum. The $\pi^-/\pi^+$ ratio is also enhanced with the soft symmetry energy at kinetic energies below 150 MeV.