Light-by-Light Scattering and Axion Like-Particle Searches in Pb+Pb Collisions at $\sqrt {s_{NN}}$ = 5.02 TeV in ATLAS Experiment at LHC

The ultra-peripheral Pb$+$Pb collisions at$\sqrt{_{SNN}}$ = 5.02 TeV recorded by the ATLAS experiment are used to study a rare light-by-light scattering process,$\gamma{\gamma}$ $\rightarrow$ $\gamma{\gamma}$, allowed in quantum electrodynamics via a loop diagram. The report summarises recent light-by-light measurements conducted using a combination of 2015 and 2018 Pb$+$Pb data sets collected by the ATLAS experiment, corresponding to an integrated luminosity of 2.2 nb$^{-1}$. The light-by-light event candidates are required to consist of only two photons produced exclusively, each with transverse energy $E{_T} >$ 2.5 GeV, pseudorapidity $|{\eta}| <$ 2.4, diphoton invariant mass $m_{\gamma{\gamma}}$ > 5 GeV, and with diphoton transverse momentum $p{_T{\gamma{\gamma}}}$ $<$ 1 GeV and acoplanarity below 0.01. The diphoton invariant mass distribution is used to set limits on the production of axion-like particles.