Spectator and participant decay in heavy ion collisions

We analyze the thermodynamical state of nuclear matter in transport calculations of heavy--ion reactions. In particular we determine temperatures and radial flow parameters from an analysis of fragment energy spectra and compare to local microscopic temperatures obtained from an analysis of local momentum space distributions. The analysis shows that the spectator reaches an equilibrated freeze-out configuration which undergoes simultaneous fragmentation. The fragments from the participant region, on the other hand, do not seem to come from a common fragmenting source, but rather heavier fragments seem to be formed earlier.