Charged particle multiplicity in Pb-Pb collisions from the NA50 experiment

Angular distributions of charged particles produced in Pb-Pb collisions at the CERN SPS have been measured by the NA50 experiment. Measurements have been performed with a silicon microstrip detector at two different beam energies (40 and 158 GeV/nucleon) and over a wide impact parameter (centrality) range. The centrality of the collision has been evaluated both by neutral transverse energy released in the interaction and by spectator nucleons energy (zero degree energy). The charged particle density at midrapidity shows a linear dependence on the number of participating nucleons at both beam energies. The particle density per participant pair and its √S dependence are also studied.