Photon--photon fusion measurements at ATLAS

Photon-photon fusion is a rare process at hadron and ion colliders. It is particularly interesting as a remarkably clean interaction with little (if any) remnant activity from the interacting particles. In this talk we present the status of photon-photon fusion measurements with the ATLAS detector. The observation of light-by-light scattering and the measurement of dimuon pairs in ultraperipheral Pb+Pb collisions are presented. The potentiel of axion-like particles searches with the upgraded ATLAS detector in Large Hadron Collider Runs 3 and 4 is reported. The ATLAS Forward Proton (AFP) detectors are used to tag intact protons from the photon-photon fusion process, that are scattered at small angles in diffractive and electromagnetic processes. These detectors can operate during standard high-luminosity LHC runs and collect large amounts of integrated luminosity. The AFP detectors and their tracking performance during 2017 and 2018 operations are presented.