Rise and fall of multifragment emission

We have studied multifragment decays of Au projectiles after collisions with C, Al, and Cu targets at a bombarding energy of 600 MeV nucleon. We find that with increasing violence of the collision, measured via the multiplicity of light particles, the mean multiplicity of intermediate-mass fragments originating from the projectile first increases to a maximum 〈${\mathit{M}}_{\mathrm{IMF}}$〉≃3 and then decreases again. Calculations using the Boltzmann-Uehling-Uhlenbeck model suggest that the fragmentation is governed by the energy ${\mathit{E}}_{\mathrm{dep}}$ deposited into the projectile spectator and that 〈${\mathit{M}}_{\mathrm{IMF}}$〉 reaches its maximum around ${\mathit{E}}_{\mathrm{dep}}$≃8 MeV/nucleon.