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Agakichiev, G.; Baur, R.; Braun-Munzinger, P.; Ceretto, F.; Drees, A.; Esumi, S.; Faschingbauer, U.; Fraenkel, Z.; Fuchs, Ch; Gatti, E.; Glässel, P.; de los Heros, C.P.; Holl, P.; Jung, Ch; Lenkeit, B.; Messer, M.; Panebrattsev, Y.; Pfeiffer, A.; Rak, J.; Ravinovich, I.; Razin, S.; Rehak, P.; Richter, M.; Sampietro, M.; Saveljic, N.; Schukraft, J.; Shimansky, S.; Seipp, W.; Socol, E.; Specht, H.J.; Stachel, J.; Tel-Zur, G.; Tserruya, I.; Ullrich, T.; Voigt, C.; Weber, C.; Wessels, J.P.; Wienold, T.; Wurm, J.P.; Yurevich, V.
Physics letters. B, 03/1998, Volume: 422, Issue: 1Journal Article
We report a measurement of low-mass electron pairs observed in 158 GeV/nucleon Pb-Au collisions. The pair yield integrated over the range of invariant masses 0.2 ≤ m≤ 2.0 GeV/c 2 is enhanced by a factor of 3.5 ± 0.4 (stat) ± 0.9 (syst) over the expectation from neutral meson decays. As observed previously in S-Au collisions, the enhancement is most pronounced in the invariant-mass region 300-700 MeV/c 2. For Pb-Au we find evidence for a strong increase of the enhancement with centrality. In addition, we show that the enhancement covers a wide range in transverse momentum, but is largest at the lowest observed p ⊥.
