LEPTON PAIR PRODUCTION BY LOW-ENERGY BREMSSTRAHLUNG IN RELATIVISTIC HEAVY-ION COLLISIONS IN 2ND-ORDER PERTURBATION-THEORY

Dileptons can be produced through the mechanism of virtual bremsstrahl ung during the deceleration of nuclei in relativistic heavy-ion collis ions. The dilepton spectrum is studied in the framework of second orde r perturbation theory. Coherence effects are found to enhance the cont ributions to pair emission through constructive interference, since th e main deceleration of nuclear matter in these collisions takes place in a small space-time region. Differential and total probabilities for lepton pairs are calculated for central U-238 + U-238 collisions at e nergies of 15 GeV/N and 60 GeV/N. Whereas the antisymmetrization of th e lepton states plays a non-negligible role for the differential proba bilities, it is not significant for the total probability.