Negative binomial multiplicity distributions in high energy hadron collisions

Abstract

This paper concerns the results recently obtained by the UA5 Collaboration on charged particle multiplicity distributions at the CERN$p\bar p$ collider$(\sqrt s = 540 GeV)$ and their comparison with lower energy data [1, 2]. Our aim is to interpret in general terms the experimental finding that the distributions are of negative binomial (NB) form both for total multiplicities and in finite pseudorapidity intervals. This can be understood in terms of partial stimulated emission of bosons, or of a simple form of cascade process, or (more artificially) with both mechanisms. The cascade interpretation appears to be the most attractive. It leads to a new concept of clustering, the empirical data imply unexpected properties for the clusters, and a novel type of high energy asymptotics seems to emerge. We briefly discuss the relation with QCD-based models for hadron production and the case ofe ⁺ e ⁻ annihilation.