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 hyperon-nucleon 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 ${\Sigma }^{-}/{\Sigma }^{+}$ and ${\Xi }^{-}/{\Xi }^0$, 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 ${\Sigma }^{-}/{\Sigma }^{+}$ 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 ${\Xi }^{-}/{\Xi }^0$ weakly depends on the symmetry energy because of the hyperon-hyperon collision mainly contributing the $\Xi$ production below the threshold energy (E${}_{th}$ = 3.72 GeV).

7 pages, 6 figures

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