Abstract
Employing thermal dilepton rates based on a medium-modified electromagnetic correlation function we show that recent dimuon spectra of the NA60 Collaboration in central In-In collisions at the CERN-SPS can be understood in terms of radiation from a hot and dense hadronic medium. Earlier calculated in-medium -meson spectral functions provide an accurate description of the data up to dimuon invariant masses of about , with good sensitivity to the predicted -meson line shape, identifying baryon-induced modifications as the prevalent ones. A reliable evaluation of the contribution enables the study of further medium effects: at masses , 4-pion type annihilation accounts for the experimentally observed excess (possibly augmented by effects of “chiral mixing”), while predictions for thermal emission from in-medium and mesons may be tested in the future.
- Received 14 March 2006
DOI:https://doi.org/10.1103/PhysRevLett.97.102301
©2006 American Physical Society