Multifragmentation induced by relativistic α-projectiles

Abstract Multifragmentation of the system α + 197 Au has been studied at incident energies of 1 and 3.6 GeV/nucleon with the new 4π setup, “FASA”. A very high mean IMF multiplicity of 〈 M 〉 IMF =5.1 ± 0.8 is observed at the higher incident energy. Applying the statistical multifragmentation model of Gross, a breakup density ϱ ϱ 0 of about 1 7 is deduced from the relative velocity between two IMFs at large relative 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. The time difference between the emission of two IMFs is less than 100 fm/c, justifying to call this process a simultaneous breakup.