BLAST OF LIGHT FRAGMENTS FROM CENTRAL HEAVY-ION COLLISIONS

The effects of collective expansion on light-fragment emission from central heavy-ion collisions are studied by carrying out calculations in a transport model with dynamic production of A less-than-or-equal-to 3 fragments. Beam energies of few hundred MeV/nucleon are considered. In the simulations the formation of a region of dense excited nuclear matter is observed, which expands in transverse directions. The expansion is reflected in the angular distributions and in the mean transverse energies of emitted fragments. At the late stage of expansion the characteristic features of local thermodynamic equilibrium are identified. Different particles share nearly the same collective energy per nucleon, and nearly the same thermal energy. The calculated mean transverse energies of the fragments reflect the collective energy whose magnitude varies with impact parameter. However, the fragment energies only partially agree with available data. The calculated spectra exhibit different slopes at angles around c.m. 90-degrees in central reactions.