Near-threshold pion production with radioactive beams at the Rare Isotope Accelerator

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 $E_{sym}(\rho )$ using the ${\pi }^{-}/{\pi }^{+}$ ratio. It is found that both the total and differential ${\pi }^{-}/{\pi }^{+}$ ratios remain sensitive to the $E_{sym}(\rho )$ when the momentum-dependence of both the isoscalar and isovector potentials are consistently taken into account. Moreover, the multiplicity and spectrum of ${\pi }^{-}$ mesons are found more sensitive to the $E_{sym}(\rho )$ than those of ${\pi }^{+}$ mesons. Finally, effects of the Coulomb potential on the pion spectra and ${\pi }^{-}/{\pi }^{+}$ ratio are also discussed.

Comments: 22 pages including 10 figures, submitted to Phys. Rev. C