Two distinct classes of alpha particles and a possible correlation of anomalously short mean free paths with the cold component

Investigation of 371 primary collisions of 56Fe on nuclear research emulsion at BEVALAC energies gives evidence for the existence of two distinct classes of reaction among the secondary alpha particles as projectile fragments. Moreover an examination of the mean free path gives a clear hint towards a correlation between an anomalously short mean free path and those α particles which belong to the cool class. (author)