Charged particle multiplicities at the CERN SPS collider

Abstract First results from UA5 on charged particle multiplicities from p p interactions at √ s = 540 GeV are presented. A value of 27.4 ± 2.0 is obtained for the mean charged multiplicity 〈 n ch 〉 of produced hadrons. This excludes an s 1 4 behaviour of 〈 n ch 〉 in going from ISR to Collider energies, but is not in disagreement with an extrapolation using a quadratic fit in ln s to previous lower energy data up to ISR energies.