DILEPTON PRODUCTION IN A CHEMICALLY EQUILIBRATING, EXPANDING, AND HADRONIZING QUARK-GLUON PLASMA

Dilepton production is considered within a complete dynamical framewor k for thermalized matter assumed to be formed in ultrarelativistic hea vy-ion collisions. Our model includes (i) chemical equilibration proce sses in the initially gluon enriched plasma, (ii) longitudinal as well as transverse expansion, and (iii) the hadronization through a mixed phase. Besides the basic electromagnetic quark-antiquark annihilation process we also take into account the QCD Compton-like and annihilatio n processes for calculating the dilepton rate in the deconfined phase, while in the hadronic stage we employ a parametrization of the effect ive form factor which is based on the complete set of meson decays and reactions. We find that, due to the transverse expansion of the matte r, the dilepton yield from the hadron gas is strongly reduced and, the refore, the deconfined matter gives the dominant contribution in case of initial conditions which are expected to be achieved at RHIC. This provides the basis for the M(perpendicular to), scaling restoration of the dilepton spectra from thermalized matter.