Centrality dependence of hadron multiplicities in nuclear collisions in the dual parton model

We show that, even in purely soft processes, the hadronic multiplicity in nucleus–nucleus interactions contains a term that scales with the number of binary collisions. In the absence of shadowing corrections, this term dominates at mid rapidities and high energies. Shadowing corrections are calculated as a function of impact parameter and the centrality dependence of mid-rapidity multiplicities is determined. The multiplicity per participant increases with centrality with a rate that increases between SPS and RHIC energies, in agreement with experiment.