Measurements of Dielectron Production in Au+Au Collisions at √sNN = 200 GeV from the STAR Experiment

Adamczyk, L. and Adkins, J. K. and Agakishiev, G. and Aggarwal, M. M. and Ahammed, Z. and Vértesi, Róbert and Csanád, Máté and Pintér, Roland László (2015) Measurements of Dielectron Production in Au+Au Collisions at √sNN = 200 GeV from the STAR Experiment. PHYSICAL REVIEW C, 92 (2). ISSN 2469-9985

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Abstract

Measurements of Dielectron Production in Au+Au Collisions at √sNN = 200 GeV from the STAR Experiment We report on measurements of dielectron (e+e−) production in Au+Au collisions at a center- of-mass energy of 200 GeV per nucleon-nucleon pair using the STAR detector at RHIC. Sys- tematic measurements of the dielectron yield as a function of transverse momentum (pT) and collision centrality show an enhancement compared to a cocktail simulation of hadronic sources in the low invariant-mass region (Mee < 1 GeV/c2). This enhancement cannot be reproduced by the ρ-meson vacuum spectral function. In minimum-bias collisions, in the invariant-mass range of 0.30 − 0.76 GeV/c2, integrated over the full pT acceptance, the enhancement factor is 1.76 ± 0.06 (stat.) ± 0.26 (sys.) ± 0.29 (cocktail). The enhancement factor exhibits weak centrality and pT dependence in STAR’s accessible kinematic regions, while the excess yield in this invariant- mass region as a function of the number of participating nucleons follows a power-law shape with a power of 1.44 ± 0.10. Models that assume an in-medium broadening of the ρ meson spectral function consistently describe the observed excess in these measurements. Additionally, we report on measurements of ω and φ-meson production through their e+e− decay channel. These mea- surements show good agreement with Tsallis Blast-Wave model predictions as well as, in the case of the φ-meson, results through its K+K− decay channel. In the intermediate invariant-mass re- gion (1.1< Mee < 3 GeV/c2 ), we investigate the spectral shapes from different collision centralities. Physics implications for possible in-medium modification of charmed hadron production and other physics sources are discussed.

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