Dilepton radiation from cascading partons in ultrarelativistic nuclear collisions

Abstract

We compute the radiation of lepton pairs by the quarks during a central collision between gold nuclei at energy of the Brookhaven Relativistic Heavy Ion Collider (\ensuremath{\surd}s =200A GeV) within the parton cascade model. The distribution of radiated pairs evolves smoothly from the initial Drell-Yan type reactions all the way towards equilibrium radiation. Contributions from reactions involving secondary partons dominate the Drell-Yan yield by at least a factor of 5 even at an invariant mass of 8 GeV. Therefore, experiments can test the evolution of partons towards thermal equilibrium at these energies.