Multiplicities and angular distributions of nucleus-nucleus interactions at SPS energies: protons to lead

Abstract

Charged particle multiplicities from high multiplicity interactions of 158 GeV/n Pb ions on Pb targets were measured in nuclear emulsion chambers. These measurements are compared to measurements of central interactions of 200 GeV/n p, O, and S beams on silver or bromine and to simulations from the FRITIOF 7.02 and Venus 4.12 Monte Carlo event generators. Multiplicities in the central region are significantly lower than either simulation predicts. Venus, the only one of the two which attempts to incorporate reinteraction phenomena, predicts a significant narrowing of the pseudorapidity distribution for the highest multiplicity events, which is not observed in the data. However, we do find evidence for unexpectedly high spectator proton transverse momenta. (6 refs)