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

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 √SNN = 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.