First results from CERES/NA45 on low-mass electron pair production in PbAu collisions

Abstract We report preliminary results of the first measurement of low-mass electron pairs in 160 GeV/nucleon PbAu collisions at central rapidities in a wide multiplicity range. This work is the continuation of our systematic studies on pair production in p-Be, p-Au and SAu interactions. The motivation for this effort derives from a new source of lowmass dileptons recently observed in SAu and S-W collisions by CERES and HELIOS/3, respectively. The results obtained in the analysis of the PbAu data confirm our previous finding that pair production in the mass range 0.2 ee c 2 is enhanced over the contributions from hadron decays while no significant excess could be observed for m ee ≲ 2m π . A comparison of the results for different multiplicity bins favours a non-linear dependence of the e + e − -yield on the accompanying charged particle densities.