Thermal Dileptons from pi - rho Interactions in a Hot Pion Gas

الأصل · EN

A systematic study of low mass dilepton production from π-ρ interactions in a hot medium is presented. Applying finite temperature perturbation theory the dilepton rate, respectively the virtual photon rate, is computed up to order gρ². For dilepton masses below the ρ the two-body reactions ππ→ ργ*, πρ→ πγ*, and the decay process ρ→ ππγ* give significant contributions. Non-equilibrium contributions to the thermal rate are estimated, including the modification of the particle distribution function with non-zero pion chemical potential. The comparison of the dilepton rate with the recent data measured in nucleus-nucleus collisions at SPS energy by the CERES Collaboration is also performed. It is shown that the additional thermal dileptons from π-ρ interactions can partially account for the access of the soft dilepton yield seen experimentally.