Low-p_T e^+e^- pair production in Au+Au collisions at sqrt{s_NN} = 200 GeV and 
U+U collisions at sqrt{s_NN} = 193 GeV at STAR

STAR Collaboration,; Adam, J.; Schmitz, N.; Seyboth, P.; et al.,

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Low-p_T e^+e^- pair production in Au+Au collisions at sqrt{s_NN} = 200 GeV and U+U collisions at sqrt{s_NN} = 193 GeV at STAR

STAR Collaboration, Adam, J., Schmitz, N., Seyboth, P., & et al. (2018). Low-p_T e^+e^- pair production in Au+Au collisions at sqrt{s_NN} = 200 GeV and U+U collisions at sqrt{s_NN} = 193 GeV at STAR. Physical Review Letters, (121), 132301. Retrieved from https://publications.mppmu.mpg.de/?action=search&mpi=MPP-2018-318.

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Datensatz-Permalink: https://hdl.handle.net/21.11116/0000-0003-F8E1-7 Versions-Permalink: https://hdl.handle.net/21.11116/0000-0003-F8E2-6

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Urheber:
STAR Collaboration¹, Autor
Adam, J.¹, Autor
Schmitz, N.¹, Autor
Seyboth, P.¹, Autor
et al.¹, Autor

Affiliations:
1Max Planck Institute for Physics, Max Planck Society and Cooperation Partners, ou_2253650

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Schlagwörter: STAR

Zusammenfassung: 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 non-central 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 ($\sqrt{\langle p^2_T\rangle}$) between 40 to 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 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 $p^{2}_{T}$ distributions.