Low-mass e(+)e(-) pair production in 158 A GeV Pb-Au collisions at the CERN SPS, its dependence on multiplicity and transverse momentum

摘要

We report a measurement of low-mass electron pairs observed in 158 GeVucleon Pb-Au collisions. The pair yield integrated over the range of invariant masses 0.2 less than or equal to m less than or equal to 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(perpendicular to). (C) 1998 Published by Elsevier Science B.V. [References: 28]