In-medium and isospin effects on particle production near threshold energies in heavy-ion collisions

Abstract

Dynamics of pseudoscalar mesons ($\ensuremath{\pi},\phantom{\rule{4pt}{0ex}}\ensuremath{\eta},\phantom{\rule{4pt}{0ex}}K$, and $\overline{K}$) and hyperons ($\mathrm{\ensuremath{\Lambda}}$ and $\mathrm{\ensuremath{\Sigma}}$) produced in heavy-ion collisions near threshold energies has been investigated within the Lanzhou quantum molecular dynamics transport model. The in-medium modifications on particle production in dense nuclear matter are implemented in the model through corrections on the elementary cross sections and by inclusion of the meson-nucleon (or hyperon-nucleon) potentials, in which the isospin effects are considered. It is found that the transportation of particles are influenced with the in-medium corrections. The total number of pions is reduced with an isospin-, density-, and momentum-dependent pion-nucleon potential. However, the ratios of charged pions is enhanced with inclusion of the potential. The production of eta in the domain of midrapidities and high momenta is sensitive to the $\ensuremath{\eta}$-nucleon potential but weakly depends on symmetry energy. The attractive antikaon-nucleon potential enhances the subthreshold $\overline{K}$ production and also influences the structure of phase-space distributions. The dynamics of etas, kaons, antikaons, and hyperons is also influenced by the pion potential because of collisions between pions and nucleons (resonances). The impacts of mean-field potentials on particle dynamics are investigated, such as the phase-space distributions from rapidity and transverse momentum spectra, inclusive invariant spectra, collective flows, etc.