Centrality in hadron-carbon, hadron-lead, and lead-lead Reactions at 158 GeV/c

Abstract

A study of centrality in p+C, π+C, p+Pb, π+Pb, and Pb+Pb reactions is made. The analysis is performed by means of a simple geometrical model. The mean number of elementary collisions, < υ>, is estimated in minimum bias p+C reactions. For the specific case of the carbon nucleus, estimates on < υ> appear to depend strongly on assumed nuclear densities. Most realistic of the presented assumptions result in a value of < υ>= 1.71 ± 0.05. Additional quantities, like predictions for the total inelastic cross-section in p+C reactions, or the number of participants in minimum bias C+C collisions, are given. The analysis is subsequently extended to minimum bias π +C, π +Pb, and p+Pb reactions. Estimates are given for the mean number of elementary collisions as well as for the contribution of single collisions P(1). A comparison with experimental data is made. Finally, the impact parameter dependence of p+Pb and Pb+Pb collisions is discussed. In view of future studies, various aspects of the analysis are discussed in detail; a bibliography of used references is included.