An exact solution of the time-dependent Dirac equation for ionization and pair production induced by ultrarelativistic heavy ion collisions is presented. Exact transition probabilities, equivalent to those that would be obtained in an untruncated basis coupled channels calculation, are presented. Exact bound-electron positron pair production probabilities are calculated to be mostly smaller tha...

The CERES/NA45 experiment measures low mass electron pair production in Pb-Au collisions at 158AGeV at the CERN SPS. In this paper, we present the electron pair enhancement in the mass range 0:2 < mee < 0:7 GeV/c 2 , it increases more than linear with charged multiplicity and is most pronounced at low pair pT < 0:5 GeV/c. Transverse mass and rapidity distributions for charged hadrons h + ? h ? ...