University of Minnesota
School of Physics & Astronomy


Low Mass Dimuons Produced in Relativistic Nuclear Collisions


by Jorg Ruppert, Charles Gale, Thorsten Renk, Peter Lichard, and Joseph Kapusta in Phys. Rev. Lett. 100, 162301 (2008)

The NA60 experiment has measured low mass muon pair production
in In-In collisions at 158A GeV with unprecedented precision. We show that
these data are reproduced very well by a dynamical model with parameters
scaled from fits to measurements of hadronic transverse mass spectra and
Hanbury Brown–Twiss correlations in Pb-Pb and Pb-Au collisions at the same
energy. The data are consistent with in-medium properties of rho and omega
mesons at finite temperature and density as deduced from empirical
forward-scattering amplitudes. Inclusion of the vacuum decay of the rho
meson after freeze-out is necessary for an understanding of the mass and
transverse momentum spectrum of dimuons with M < 0.9 GeV/c2.

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