LEPTON PAIRS FROM THERMAL MESONS

We study the net dielectron production rates from an ensemble of thermal mesons, using an effective Lagrangian to model their interaction. The coupling between the electromagnetic and the hadronic sectors is done through the vector meson dominance approach. For the first time, a complete set of light mesons is considered. We include contributions from decays of the type V(P) --> P(V) + e+e-, where V is a vector meson and P is a pseudoscalar, as well as those from binary reactions P + P, V + V, and V + P --> e+e-. Direct decays of the type V --> e+e- are included and shown to be important. We find that the dielectron invariant mass spectrum naturally divides into distinct regions: in the low mass domain the decays from vector and pseudoscalar mesons form the dominant contribution. The pion-pion annihilation and direct decays then pick up and form the leading signal in an invariant mass region that includes the rho-omega complex and extends up to the phi. Above the invariant mass M almost-equal-to 1 GeV other two-body reactions take over as the prominent mechanisms for lepton pair generation. These facts will have a quantitative bearing on the eventual identification of the quark-gluon plasma.