Energy dependence of multiplicity in proton-nucleus collisions and models of multiparticle production

Abstract

This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett. 50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratio R_em = <n_s>/<n_ch>, where <n_ch> is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1.6 at 68 GeV/c and attains a constant value of 1.71 ± 0.04 in the region 200 to 8000 GeV/c. Furthermore, R_em = 1·71 implies an effective A-dependence of R_A =A ^0.18,i.e., a very weak dependence. Predictions of R em on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production.