Reexamining lepton pairs at ultrarelativistic energies

We confirm the importance of standard medium effects (hadronic rescattering) in heavy-ion collisions by using a perturbative-QCD-motivated hadronic model to investigate the dilepton spectra from Pb+Au collisions at 158 GeV/nucleon. These same effects, namely, prompt πρ⃗πe⁺e^-, have been studied in several CERN SPS systems [J. Murray, W. Bauer, and K. Haglin, Phys. Rev. C 57, 882 (1998)]. The results presented here are consistent with previous studies stating that this type of rescattering effect explains a portion of the “excess” lepton pairs seen by the CERES experiment, but not the entire effect.