Dielectron Mass Spectra from Au plus Au Collisions at root s(NN)=200 Ge V

Adamczyk, L. and Adkins, J. K. and Agakishiev, G. and Aggarwal, M. M and Ahammed, Z. and Alekseev, I. and Alford, J. and Anson, C. D. and Aparin, A. and Arkhipkin, D. and Aschenauer, E. C. and Averichev, G. S. and Banerjee, A. and Barnovska, Z. and Beavis, D. R. and Bellwied, R. and Bhasin, A. and Bhati, A. K. and Bhattarai, P. and Bichsel, H. and Bielcik, J. and Bielcikova, J. and Bland, L. C. and Bordyuzhin, I. G. and Borowski, W. and Bouchet, J. and Brandin, A. V. and Brovko, S. G. and Bultmann, S. and Bunzarov, I. and Vértesi, Róbert (2014) Dielectron Mass Spectra from Au plus Au Collisions at root s(NN)=200 Ge V. PHYSICAL REVIEW LETTERS, 113 (2). ISSN 0031-9007

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Abstract

We report the STAR measurements of dielectron (e+e−) production at midrapidity (|yee| <1) in Au+Au collisions at √sNN = 200 GeV. The measurements are evaluated in different invariant mass regions with a focus on 0.30-0.76 (ρ-like), 0.76-0.80 (ω-like), and 0.98-1.05 (φ-like) GeV/c2. The spectrum in the ω-like and φ-like regions can be well described by the hadronic cocktail simulation. In the ρ-like region, however, the vacuum ρ spectral function cannot describe the shape of the dielectron excess. In this range, an enhancement of 1.77±0.11(stat.)±0.24(sys.)±0.33(cocktail) is determined with respect to the hadronic cocktail simulation that excludes the ρ meson. The excess yield in the ρ-like region increases with the number of collision participants faster than the ω and φ yields. Theoretical models with broadened ρ contributions through interactions with constituents in the hot QCD medium provide a consistent description of the dilepton mass spectra for the measurement presented here and the earlier data at the Super Proton Synchrotron energies.

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