Nuclear interactions and primary cosmic-ray component around 1015 eV viewed through the cluster analysis of -ray families

An analysis of the -ray families (E100 TeV) obtained with the Mt. Fuji emulsion chambers was made focusing attention on the cluster structure of families, and the validity of scaling in the fragmentation region in the 1015-eV region was examined by comparing the results with those of artificial families. We deduced that (i) scaling in the fragmentation region (Feynman x>0.1) is not broken appreciably, at least below 1015 eV, (ii) scaling in the central region (x<<0.1) seems to be broken largely at E>1015 eV; multiplicity increases proportionally to E14 or even stronger (say, E13), (iii) the iron component in the primary cosmic rays rapidly increases and occupies 60-70% of the total flux at 1015 eV and that of the protons decreases to f 10%, and (iv) the average transverse momentum of produced pions in the fragmentation region stays within 400 MeV/c.