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Volume 345 - International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions (HardProbes2018) - Electroweak Probes
Low-$p_{\rm T}$ $e^+e^-$ pair production in Au+Au collisions at $\sqrt{s_{\rm NN}}$= 200 GeV and U+U collisions at $\sqrt{s_{\rm NN}}$ = 193 GeV at STAR
S. Yang
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Pre-published on: 2019 January 11
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Abstract
We present the first measurement of $e^+e^-$ pair production at $p_T$ < 0.15 GeV/$c$ in Au$+$Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV and U$+$U collisions at $\sqrt{s_{\rm NN}}$= 193 GeV with the STAR experiment. Significant enhancement with respect to known hadronic contributions is observed in the 40-80% centrality class of these collisions. The yield excess peaks distinctly at low $p_T$ with a width ($\sqrt{\langle p^2_T\rangle}$) between 40 and 60 MeV/$c$. Model calculations of photon-photon interaction describe the observed excess yields but fail to reproduce the $p^{2}_{T}$ distributions.
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