Comprehensive Interpretation of Thermal Dileptons Measured at the CERN Super Proton Synchrotron

Hendrik van Hees and Ralf Rapp
Phys. Rev. Lett. 97, 102301 – Published 8 September 2006

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 ρ-meson spectral functions provide an accurate description of the data up to dimuon invariant masses of about M0.9GeV, with good sensitivity to the predicted ρ-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 M>0.9GeV, 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 ω and ϕ mesons may be tested in the future.

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  • Received 14 March 2006

DOI:https://doi.org/10.1103/PhysRevLett.97.102301

©2006 American Physical Society

Authors & Affiliations

Hendrik van Hees and Ralf Rapp

  • Cyclotron Institute and Physics Department, Texas A & M University, College Station, Texas, 77843-3366 USA

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Issue

Vol. 97, Iss. 10 — 8 September 2006

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