2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/103932The NA60 experiment has studied low-mass muon pairs in 158 AGeV Indium-Indium collisions at the CERN SPS. A strong excess of pairs is observed above the expectation from neutral meson decays. The unprecedented sample size of 360 000 events and the good mass resolution of about 2% allow to isolate the excess by subtraction of the known sources. The shape of the resulting mass spectrum is consistent with a dominant contribution from pi+ pi- -> rho -> mu+ mu- annihilation. The associated rho spectral function shows a strong broadening, but essentially no shift in mass.4 pages, 3 figures, Proceedings of Quark Matter 2005, BudapestNuclear Experimenttext