Modifications of the pion-production threshold in the nuclear medium in heavy ion collisions and the nuclear symmetry energy Academic Article uri icon


  • 2015 American Physical Society. Using the relativistic Vlasov-Uehling-Uhlenbeck (RVUU) equation based on mean fields from the nonlinear relativistic NL and NL models, which have same nuclear equation of state and symmetry energy but different symmetry energy slope parameters, we study the effect of medium modification of the pion-production threshold on the total pion yield and the -/+ ratio in Au+Au collisions. We find that the in-medium threshold effect enhances both the total pion yield and the -/+ ratio, compared to those without this effect. Furthermore, including the medium modification of the pion-production threshold leads to a larger -/+ ratio for the NL model with a larger symmetry energy parameter than the NL model with a smaller symmetry energy parameter, opposite to that found without the in-medium threshold effect. To reproduce the total pion yield measured by the FOPI Collaboration, we introduce a density-dependent cross section for baryon production from nucleon-nucleon collisions, which suppresses the total pion yield but hardly changes the -/+ ratio. Because of the small difference in the stiffness of their symmetry energies, the -/+ ratios obtained from both the NL and NL models are consistent with the FOPI data within the experimental errors.

published proceedings

  • Physical Review C

author list (cited authors)

  • Song, T., & Ko, C. M.

citation count

  • 57

complete list of authors

  • Song, Taesoo||Ko, Che Ming

publication date

  • January 2015