We report systematic measurements of dielectron (e±e±) invariant-mass Mee spectra at mid-rapidity in Au+Au collisions at √sNN = 27, 39, and 62.4 GeV taken with the STAR detector at the Relativistic Heavy Ion Collider. For all energies studied, a significant excess yield of dielectrons is observed in the low-mass region (0.40< Mee < 0.75 MeV/c2) compared to hadronic cocktail simulations at freeze-out. Models that include an in-medium broadening of the ρ-meson spectral function consistently describe the observed excess. In addition, we report acceptance-corrected dielectron-excess spectra for Au+Au collisions at mid-rapidity (|yee| < 1) in the 0−80% centrality bin for each collision energy. The integrated excess yields for 0.4 < Mee < 0.75 GeV/c2, normalized by the charged particle multiplicity at mid-rapidity, are compared with previously published measurements for Au+Au at √sNN = 19.6 and 200 GeV. The normalized excess yields in the low-mass region show no significant collision energy dependence. The data, however, are consistent with model calculations that demonstrate a modest energy dependence.
|Original language||English (US)|
|State||Published - Oct 23 2018|
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