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Non-perturbative finite $T$ broadening of the $ρ$ meson and dilepton emission in heavy ion-collisions

We study self-consistently the finite $T$ broadening of the $ρ$-meson and its implications for dilepton emission in heavy ion-collisions. For this purpose finite width effects at finite temperature due to the $ρ$-$π$ interaction are investigated in a self-consistent $Φ$-functional approach. The temperature dependence of the $ρ$-meson and pion spectral functions and self-energies is discussed. The spectral functions show considerable broadening in comparison with a perturbative calculation on the one-loop level. Using these spectral functions, we make a comparison to dilepton emission data from the CERES NA49 collaboration employing a parametrized fireball evolution model of collision. We demonstrate that these non-perturbative finite width effects are in-medium modifications relevant to the understanding of the enhancement of the low invariant mass spectrum of dileptons emitted in A-A collisions.