Measurements of dielectron production in Au + Au collisions at √sNN=200 GeV from the STAR experiment

Adamczyk, L. and Planinić, Mirko and Poljak, Nikola and Zyzak, M. (STAR Collaboration) (2015) Measurements of dielectron production in Au + Au collisions at √sNN=200 GeV from the STAR experiment. Physical Review C, 92 (2). pp. 24912-35. ISSN 0556-2813

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Abstract

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 BNL Relativistic Heavy Ion Collider. Systematic measurements of the dielectron yield as a function of transverse momentum (p_T) and collision centrality show an enhancement compared to a cocktail simulation of hadronic sources in the low invariant-mass region (M_ee<1GeV/c^2). This enhancement cannot be reproduced by the ρ-meson vacuum spectral function. In minimum-bias collisions, in the invariant-mass range of 0.30–0.76GeV/c^2, 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 measurements 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 region (1.1<M_ee<3GeV/c^2), 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.

Item Type: Article
Date: 24 August 2015
Subjects: NATURAL SCIENCES > Physics > Nuclear Physics
Additional Information: Copyright (2015) by the American Physical Society. Received 9 April 2015; Published 24 August 2015.
Divisions: Faculty of Science > Department of Physics
Publisher: American Physical Society
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 22 Sep 2015 14:42
Last Modified: 22 Sep 2015 14:48
URI: http://digre.pmf.unizg.hr/id/eprint/4235

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