Medium Modifications of the Rho Meson at CERN/SPS Energies

Abstract

Rho meson propagation in hot hadronic matter is studied in a model with coupling to $\pi \pi$ states. Medium modifications are induced by a change of the pion dispersion relation through collisions with nucleons and ${\Delta }^{\prime }s$ in the fireball. Maintaining gauge invariance dilepton production is calculated and compared to the recent data of the CERES collaboration in central S+Au collisions at 200 GeV/u. The observed enhancement of the rate below the rho meson mass can be largely accounted for.

Comments: 10 pages RevTeX and 2 figures (uuencoded .ps-files)