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Joe Kapusta University of Minnesota Radiation of dileptons and photons from high energy nuclear collisions provides information on the space-time evolution of the hot dense matter produced in these collisions. We compute this radiation using relativistic hydrodynamics and a coarse-grained version of the microscopic event generator UrQMD, both of which provide a good description of the hadron spectra. Comparisons are made to data on central Pb-Pb and Pb-Au collisions taken at the CERN SPS at a beam energy of 158 A GeV. Both hydrodynamics and UrQMD provide very good descriptions of the photon transverse momentum spectrum measured between 1 and 4 GeV, but slightly underestimate the low mass spectrum of electron-positron pairs, even with greatly broadened rho and omega vector mesons.
Tuesday, March 19th 2002, 12:00 |