STATISTICAL FRAGMENTATION OF AU PROJECTILES AT E/A=600 MEV

The mean multiplicity of intermediate mass fragments (IMF) [M(IMF)] produced by fragmentation of Au projectiles interacting with targets of C, Al, Cu, and Pb at an incident energy of E/A =600 MeV is compared to predictions of statistical multifragmentation and sequential evaporation models. The initial conditions for the calculations were provided by Boltzmann-Uehling-Uhlenbeck simulations. In the high excitation energy regime where the IMF multiplicity reaches its maximum the observed universal correlation between [M(IMF)] and the total charge Z(bound) of projectile fragments with charges Z greater-than-or-equal-to 2 cannot be reproduced by a sequential evaporation code. In this regime the data are better described by statistical decay calculations which assume the formation of an expanded nuclear system and a rather fast breakup.