Light-by-light scattering in lead-lead collisions in the ATLAS experiment

Light-by-light (LbyL) scattering, $\gamma\gamma\rightarrow\gamma\gamma$, is a quantum-mechanical process, forbidden by the classical theory of electrodynamics. Despite the small cross-section, it is theoretically possible to observe this process in ultra-peripheral high energy heavy-ion collisions. Based on 0.48 nb$^{-1}$ of 2015 Pb+Pb data, a first direct evidence of LbyL scattering was found by the ATLAS Collaboration in 2017. In total, 13 events were found in the signal region with a background expectation of 2.6$\pm$0.7 events. The excess corresponds to 4.4$\sigma$ significance over the background-only hypothesis. In November 2018, the new dataset of Pb+Pb collisions was collected by the ATLAS experiment with an integrated online luminosity of 1.7 nb$^{-1}$. The control distributions for $\gamma\gamma\rightarrow e^+e^-$ events are presented for the new data.