Initial electromagnetic field dependence of photon-induced production in isobaric collisions at STAR

¹ Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China
² State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei 230026, China

^* e-mail: skfwyl@mail.ustc.edu.cn

Published online: 1 March 2023

Abstract

In these proceedings, we present the measurements of e⁺e⁻ pair production at very low transverse momentum in ₄₄⁹⁶Ru + ₄₄⁹⁶Ru and ₄₀⁹⁶Zr + ₄₀⁹⁶Zr collisions at √S_NN = 200 GeV by the STAR experiment. The electromagnetic field dependence of photon-induced production is studied for the first time, via comparisons between the measurements in isobaric collisions to the published results in Au+Au and U+U collisions. Taken the initial electromagnetic field dependence into account, the excess yield of e⁺e⁻ pair production shows an impact parameter dependence. The results are also compared to model calculations based on EPA-QED, which describe the observed excess yields for different collision species.