High-density symmetry energy from subthreshold hyperon production in heavy-ion collisions

Abstract

The hyperon dynamics in heavy-ion collisions near threshold energy has been investigated within the quantum molecular dynamics transport model. The isospin and momentum dependent hyperonnucleon potential and the threshold energy correction on the hyperon elementary cross section are included in the model. It is found that the high-density symmetry energy is dependent on the isospin ratios Σ − /Σ + and Ξ − /Ξ 0 , in particular in the domain of high kinetic energies. The isospin diffusion in heavy-ion collisions influences the neutron/proton ratio in the high-density region. The Σ − /Σ + ratio depends on the stiffness of symmetry energy, in particular at the beam energy below the threshold value (E th =1.58 GeV), i.e., the kinetic energy spectra of the single ratios, excitation functions and energy spectra of the double ratios in the isotopic reactions of 108 Sn + 112 Sn, 112 Sn + 112 Sn, 124 Sn + 124 Sn and 132 Sn + 124 Sn. The double strangeness ratio Ξ − /Ξ 0 weakly depends on the symmetry energy because of the hyperon-hyperon collision mainly contributing the Ξ production below the threshold energy (E th = 3.72 GeV).