Multiplicity Distribution in Hadron-Nucleus Collisions

Abstract

Charged particle multiplicity distribution in proton emulsion and pion-neon collisions have been calculated on the basis of two step production mechanisms for the secondary particles. It has been compared with the experimental results to see if the emission of secondaries from the different excited centres inside the target nucleus is correlated or uncorrelated. It is found that the experimentally observed forward-backward asymmetry in the charged secondaries in P-P collisions falls short of explaining the multiplicity distribution in hadron-nucleus collisions. Probability distribution for the number of collisions made by hadrons inside various nuclei is also given. §I. Introduction It has been fairly well established that the multiplicity in hadron-nucleus collisions shows only a weak dependence on the mass number A of the target nucleus. Recent studies 1l, 2l with nuclear emulsions exposed to accelerator beams clearly show that if we exclude the coherent production processes, then the results indicate the concentration of the nuclear multiplication effects more or less in the target fragmentation region only. As a matter of fact the indication for such a trend came from early cosmic ray experiments. 3l The results of such experiment 4l, 5l are summarized in Table I; the corresponding log tan{} distribution is given in Fig. 1. The inference one can draw from this data is that if one goes from a light target like carbon to a heavier one like brass, then there is no increase in the number of secondaries in the forward hemisphere of the c.m. system (which cor­ responds to the beam fragmentation region). Whatever increase occurs in the number of secondary particles is in the backward hemispheres of the c.m. system which corresponds to the target fragmentation region. There have been quite a few attempts during the last few years 6J-g) where one has used the results from hadron-nucleus collisions to test the validity of different models like the multiperipheral, diffraction dissociation, the nova and the fragmen­ tation, etc. and also new models 10l have been put forward to explain the observed features in the angular distribution and multiplicity of charged secondaries in colli­ sions involving nuclei (for more details see Refs. 11) and 12)). In this paper, assuming a simple picture for the collisions involving nuclei, we calculate the charged multiplicity distribution in such collisions and compare it with the observed one. This is done for proton-emulsion and pion-neon collisions, since we have