Dimuon and charm production in In+In collisions at the CERN SPS

The NA60 experiment studies muon pair production with proton and Indium beams. It is a second generation experiment, designed to answer specific questions left open, in the leptonic sector, by the previous round of SPS experiments, finished in 2000. The results presented in this paper cover the dimuon invariant mass range from the threshold to the J/ψ. The main physics topics that we address include the in-medium modifications of the ρ meson, the origin of the dimuon excess observed between the ϕ and the J/ψ, and the study of the anomalous J/ψ suppression. For each of these subjects, the NA60 results represent a significant step forward towards a deeper understanding of the physics of heavy ion collisions at SPS energies.