Searching for anomalous Higgs boson decays into two axions in four photon final states with the ATLAS detector

A dedicated search for anomalous Higgs boson decays into two axion-like-particles (ALPs) is presented, using the full Run-2 data-set recorded by the ATLAS experiment. The ALPs are assumed to decay into two photons, providing sensitivity to various recently proposed models that could explain the famous g-2 discrepancy. This poster presents details of the search in the mass range of ALPs between 100 MeV and 5 GeV the signature includes highly collinear photons. A dedicated identification of collinear photons was developed and is presented along with the upper limits placed on the branching ratio of the Higgs boson to the the four photon final state.