Experimental results on the multiplicity distributions and correlations between various types of secondary particles are presented for 800 GeV proton-emulsion nucleus interactions. The results indicate strong correlation between the shower and the grey particles and an independence of the normalised multiplicity with respect to the target mass. The number of grey particles in an interaction is found to be the best experimental measure of the number of intranuclear collisions.

The validity of various available methods for the estimation of the primary energy in proton–nucleon and proton–nucleus interactions has been examined by using the data of the highest available machine energy for fixed targets, i.e., 800 GeV. To test the different methods for primary-energy determination for various subsamples, the data was divided into different secondary-particle multiplicity groups. It was found that Castagnoli's method (C. Castagnoli, G. Cortini, C. Franzinetti, A. Mannfredini, and A. Moreno. Nuovo Cimento, 10, 1539 (1953)). yields the best results for energy estimation for proton–nucleon collisions while the method of Gibbs et al. (R. E. Gibbs, J. R. Florian, L. D. Kirkpatrick, J. J. Lord, and J. W. Martin. Phys. Rev. D, (10, 783 (1974)). yields the best results for proton–nucleus collisions.