CERES results on low-mass electron pair production in PbAu collisions

Abstract The CERES/NA45 collaboration measured, at the CERN SPS, low-mass electron pair production in Pb Au collisions at 158 A GeV/c incident momentum. In this paper we present an analysis of the data taken during the SPS Pb-beam period in the fall of 1995. The results confirm previous findings of CERES showing that the pair production in the mass range 0.2 ee 2 , when scaled to the ion case with the event multiplicity, is enhanced over the expected yield from the known hadronic sources in pp collisions. A comparison of the results for different multiplicity bins indicates that the excess increases faster than linearly with charged-particle multiplicity. We also present the transverse-momentum distributions of the observed pairs.