Time scale of multifragment emission in 4He + Au collisions at E/A = 3.65 GeV/nucleon

The relative angular distribution of coincident intermediate mass fragments (IMF) is studied for 4He + Au collisions at 3.65 GeV/nucleon with the new 4π setup FASA installed at the JINR synchrophasotron. Strong suppression of small relative angles is observed, which is attributed to the mutual Coulomb repulsion of emitted fragments. The multibody Coulomb trajectory calculations are performed on an event-by-event basis, varying the decay lifetime of the fragmenting system as a parameter. The initial configurations for these calculations - fragment masses, charges, starting positions, and velocities - are calculated in the statistical multifragmentation model. The charges, masses, and excitation energies of the fragmenting nuclei are estimated in the intranuclear cascade approach. It is shown that the relative angular distribution of IMFs is very sensitive to the time scale of the multifragmentation process. The experimental data are well described assuming breakup of the system with less than 100 fm/c mean lifetime. 26 refs., 5 figs