STATISTICAL MULTIFRAGMENTATION

Two scenarios for the fragmentation of nuclei in collisions at interme diate energies are conceivable: A fast direct ''shattering'' or ''abra sion - ablation'' of a cluster has frequently been proposed in high-en ergy nuclear collisions. On the other hand there is an increasing numb er of data that suggest a nearly complete equilibration of the excited system before it breaks ''simultaneously'' into several pieces. The s ize-distribution, the size-correlations, the energy-spectra as well as the angular distributions are consistent with a loss of memory of the entrance channel. Because the latter scenario is ruled by the accessi ble phase-space and therefore by thermodynamics of a closed small syst em, which is a challenging problem of its own right, we treat only the statistical fragmentation of small equilibrized sources. A very simil ar situation is expected of the fragmentation of multiply charged meta l clusters like Na-n(z+). With the help of Microcanonical Metropolis-M onte Carlo (MMMC) we study multifragmentation as a realistic example o f thermodynamics of a finite many-body system subjected to long-range forces using the most basic prinicples of statistical physics. MMMC is an alternative to molecular dynamics but it has the advantage that on e only samples the final states one is interested in and to get the re levant branching ratios.