Semi-Inclusive Rapidity Distributions from a Longitudinal Phase Space

Abstract

Single particle rapidity distributions in events with fixed multiplicities are calculated using a longitudinal phase space model with a constant transverse momentum. Two cases (1) pion-pion collisions with no leading pions (or e+-eannihilation into pions) and (2) nucleon-nucleon collisions with leading nucleons are considered and numerical results are given for the c.m. total energy W =540 GeV. In Case (1), sharp peaks appear at the ends of the available rapidity space when the multiplicity n is less than 13 while the peaks disappear and a fiat plateau develops when 15:S n:S 60. The plateau changes into a smooth bump as n increases further. In Case (2), both peaks at low n and a plateau at medium n are smeared out considerably by the leading particle effect, and a smooth bump dominates for almost all range of n. Prominent dips observed experimentally in the pseudorapidity distributions for low n are not reproduced in the calculated rapidity distributions.