Nonequilibrium description of dilepton production in heavy ion reactions

Abstract

Time dependent medium modifications of low mass vector mesons are investigated within a nonequilibrium quantum field theoretical description on the basis of the Kadanoff-Baym equations. Time scales for the adaption of the spectral properties to changing self energies are given and, under use of a model for the fireball evolution, nonequilibrium dilepton yields from the decay of ρ- and ω-mesons are calculated. Comparison of the results with calculations that assume instantaneous adaption to the changing medium show that the consideration of memory effects is important.