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arXiv · 2308.03070

The effect of initial nuclear deformation on dielectron photoproduction in hadronic heavy-ion collisions

Jiaxuan. Luo·Xinbai. Li·Zebo. Tang·Xin. Wu·Wangmei. Zha
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Abstract

Significant excesses of $e^+e^-$ pair production at very low transverse momentum ($p_T <$ 0.15 GeV/c) were observed by the STAR collaboration in hadronic heavy-ion collisions. Such enhancement is assumed to be a sign of photon-photon production in heavy-ion collisions with hadronic overlap, based on comparisons with model calculations for spherical Au + Au collisions. However, there is a lack of calculations for $e^+e^-$ pair production from coherent photon-photon interactions in hadronic U + U collisions, due to the deformity of Uranium nuclei. In this article, we present calculations for $e^+e^-$ pair photoproduction at $\sqrt{s_{NN}}$ = 193 GeV in both spherical and deformed U + U collisions within STAR detector acceptance using the equivalent photon approximation (EPA). We conduct event-by-event analysis to investigate the effects of initial nuclear deformation on pair production. Our numerical results show good agreement with experimental data for the 40%--60% and 60%--80% centrality classes in U + U collisions, and the differences between spherical and deformed configurations are approximately 3\%. We also calculate the yields of the photoproduced $e^+e^-$ pair in hadronic deformed Ru + Ru and Zr + Zr collisions at $\sqrt{s_{NN}}$ = 200 GeV. The results reveal that the ratios of the yields of Ru to Zr exhibit very small differences ($<$ 1%) between spherical and deformed cases.

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Jiaxuan. Luo, Xinbai. Li, Zebo. Tang, Xin. Wu, Wangmei. Zha. 2023-08-06. The effect of initial nuclear deformation on dielectron photoproduction in hadronic heavy-ion collisions. https://doi.org/10.1103/physrevc.108.054906

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