Mean free path of relativistic fragments from heavy ion reactions induced by 1.8A GeV 40Ar in low sensitive nuclear emulsions

Preliminary data is given for the mean free path of projectile-like fragments, 2 less than or equal to Z less than or equal to 18, emitted in 40Ar induced heavy ion reactions in nuclear emulsions at 1.8A GeV as well as in later generations of fragmentation chains. Only within a distance of one cm or less from the interaction point do we observe an enhanced collision frequency. If this observation is a signal of an anomalous fragmentation component this must have a very short mean free path or a lifetime less than 10-11 s. Some suggestions are given for systematic or statistical effects which could also possibly explain our results