Low-<i>p<sub>T</sub></i> <i>e</i><SUP>+</SUP><i>e</i><SUP>-</SUP> Pair Production in Au plus Au Collisions at √<i>s<sub>NN</sub></i>=200 GeV and U plus U Collisions at √<i>s<sub>NN</sub></i>=193 GeV at STAR



Adam, J, Adamczyk, L, Adams, JR, Adkins, JK, Agakishiev, G, Aggarwal, MM, Ahammed, Z, Ajitanand, NN, Alekseev, I, Anderson, DM
et al (show 335 more authors) (2018) Low-<i>p<sub>T</sub></i> <i>e</i><SUP>+</SUP><i>e</i><SUP>-</SUP> Pair Production in Au plus Au Collisions at √<i>s<sub>NN</sub></i>=200 GeV and U plus U Collisions at √<i>s<sub>NN</sub></i>=193 GeV at STAR. PHYSICAL REVIEW LETTERS, 121 (13). 132301-.

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Abstract

We report first measurements of e^{+}e^{-} pair production in the mass region 0.4<M_{ee}<2.6  GeV/c^{2} at low transverse momentum (p_{T}<0.15  GeV/c) in noncentral Au+Au collisions at sqrt[s_{NN}]=200  GeV and U+U collisions at sqrt[s_{NN}]=193  GeV. Significant enhancement factors, expressed as ratios of data over known hadronic contributions, are observed in the 40%-80% centrality of these collisions. The excess yields peak distinctly at low p_{T} with a width (sqrt[⟨p_{T}^{2}⟩]) between 40 and 60  MeV/c. The absolute cross section of the excess depends weakly on centrality, while those from a theoretical model calculation incorporating an in-medium broadened ρ spectral function and radiation from a quark gluon plasma or hadronic cocktail contributions increase dramatically with an increasing number of participant nucleons. Model calculations of photon-photon interactions generated by the initial projectile and target nuclei describe the observed excess yields but fail to reproduce the p_{T}^{2} distributions.

Item Type: Article
Uncontrolled Keywords: STAR Collaboration
Depositing User: Symplectic Admin
Date Deposited: 07 May 2019 10:14
Last Modified: 11 Oct 2023 00:25
DOI: 10.1103/PhysRevLett.121.132301
Open Access URL: https://doi.org/10.1103/PhysRevLett.121.132301
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3040055