POWER LAWS FOR RATIOS OF MOMENTS OF THE FRAGMENT SIZE DISTRIBUTION

The method of scaled factorial moments (s.f.m.) is used to study fluctuations of the fragment size distribution in the percolation model and in nuclear multifragmentation following the breakup of the high energy nuclei. It is found that similarly as in several cascade models describing multiparticle production at ultrarelativistic energies, the site-bond percolation model at around the critical point for large lattice sizes exhibits a power behaviour of the ratio of s.f.m. of different rank. Both the experimental data and the percolation model events selected according either to the number of intermediate mass fragments or to the total fragment multiplicity can be fitted well by such a power behaviour. Together with evidence for an intermittent pattern of fluctuations which was found earlier in the fragment charge/mass distributions at E/A approximately 1 GeV/nucleon the present results strongly suggests not only self-similarity in the fragment size distribution and a random character for the scaling law but also the importance of the branching mechanism in the fragment formation process.