Hyperon Dynamics in Heavy-Ion Collisions near Threshold Energy

Within the framework of quantum molecular dynamics transport model, the isospin and in-medium effects on the hyperon production in the reaction of Au-197 + Au-197 are investigated thoroughly. A repulsive hyperon-nucleon potential from the chiral effective field theory is implemented into the model, which is related to the hyperon momentum and baryon density. The correction on threshold energy of the elementary hyperon cross section is taken into account. It is found that the sigma yields are suppressed in the domain of midrapidity and kinetic energy spectra with the potential. The hyperons are emitted in the reaction plane because of the strangeness exchange reaction and reabsorption process in the nuclear medium. The sigma (-)/sigma (+) ratio depends on the stiffness of nuclear symmetry energy, in particular in the high-energy region (above 500 MeV).