Near-threshold pion production with radioactive beams

Abstract

Using an isospin- and momentum-dependent transport model we study near-threshold pion production in heavy-ion collisions induced by radioactive beams at the planned rare isotope accelerator (RIA). We revisit the question of probing the high-density behavior of nuclear symmetry energy ${E}_{\mathrm{sym}}(\ensuremath{\rho})$ using the ${\ensuremath{\pi}}^{\ensuremath{-}}/{\ensuremath{\pi}}^{+}$ ratio. It is found that both the total and differential ${\ensuremath{\pi}}^{\ensuremath{-}}/{\ensuremath{\pi}}^{+}$ ratios remain sensitive to the ${E}_{\mathrm{sym}}(\ensuremath{\rho})$ when the momentum-dependence of both the isoscalar and isovector potentials are consistently taken into account. Moreover, the multiplicity and spectrum of ${\ensuremath{\pi}}^{\ensuremath{-}}$ mesons are found more sensitive to the ${E}_{\mathrm{sym}}(\ensuremath{\rho})$ than those of ${\ensuremath{\pi}}^{+}$ mesons. Finally, effects of the Coulomb potential on the pion spectra and ${\ensuremath{\pi}}^{\ensuremath{-}}/{\ensuremath{\pi}}^{+}$ ratio are also discussed.