Multifragmentation of Big Nuclei

Abstract

Heavy target nuclei split into many fragments when bombarded by protons or heavy ions at very high energies (Ep > 10 GeV). A statistical model is presented, which calculates the relative phase-space available for the various multifragment decay channels. It is shown that the Coulomb-interaction between the fragments is crucial. Including it by a self-consistent mean field method leads to a significant enhancement of the survival of the most heavy fragments and a strong suppression of the probability for splitting into many medium fragments. At a temperature of ∼ 5 MeV an U-shaped mass-yield curve results from the model calculations for most of the heavy targets, whereas they show a clear fission peak for U-targets. Over the whole fragment-mass region the experimental mass-yield distributions for limiting fragmentation can thus be reproduced. Further investigations and refinements of the model are needed before a final judgement about the importance of the multi-fragment phase-space relative to dynamical effects is possible.