Features of pC interactions at a momentum of 4.2 GeV/c versus the degree of centrality of collisions between protons and carbon nuclei: Multiplicity of secondary particles
Abstract
New experimental data obtained for the multiplicities of charged pions and protons from the interaction of 4.2-GeV/c protons with a carbon nucleus by using the 2-m propane bubble chamber installed at the High Energy Laboratory (Joint Institute for Nuclear Research, Dubna) are presented versus the degree of collision centrality. The parameter Q defined for each individual event as the difference of the total multiplicities of positively and negatively charged particles without allowing for the multiplicity of evaporated protons whose momentum is less than 0.3 GeV/c is taken for a criterion of the degree of collision centrality. It is shown that, with increasing Q, the multiplicity of positively charged pions and the multiplicity of participant protons from the target nucleus grow considerably; concurrently, the multiplicity of negatively charged pions remains at nearly the same level, while the mean multiplicity of evaporated protons decreases sharply. Our experimental data are compared with the results of calculations based on the cascade-evaporation model and the modified FRITIOF model. Within the FRITIOF model, nonnucleon degrees of freedom in nuclei (Δ+, Δ0 isobars) are taken into account for the first time, and the resulting description of the features of secondary particles appears to be by and large satisfactory.