Source Temperatures and Sizes in Central Collisions

Abstract

For midrapidity fragments from central 50-200 AMeV Au+Au collisions temperatures from double ratios of isotopic yields were compared with temperatures from particle unbound states. Temperatures from particle unbound states with T = 4-5 MeV show with increasing beam energy an increasing difference to temperatures from double ratios of isotopic yields, which increase from T = 5MeV to T = 12MeV. The lower temperatures extracted from particle unstable states can be explained by increasing cooling of the decaying system due to expansion. This expansion is driven by the radial flow, and freeze out of particle unstable states might depend on the dynamics of the expanding system. Source sizes from pp-correlation functions were found to be 9 to 11 fm.