MULTIFRAGMENTATION INDUCED BY RELATIVISTIC ALPHA-PROJECTILES

Multifragmentation of the system alpha + Au-197 has been studied at in cident energies of 1 and 3.6 GeV/nucleon with the new 4 pi setup, ''FA SA''. A very high mean IMF multiplicity of < M >(IMF) = 5.1 +/- 0.8 is observed at the higher incident energy. Applying the statistical mult ifragmentation model of Gross, a breakup density rho/rho(0) of about 1 /7 is deduced from the relative velocity between two IMFs at large rel ative angles. The excitation energy increases from 4.5 MeV/nucleon at the lower beam energy to 5.5 MeV/nucleon at the higher beam energy. Th e time difference between the emission of two IMFs is less than 100 fm /c, justifying to call this process a simultaneous breakup.