Two-Photon Measurements in ATLAS

At the Large Hadron Collider, two-photon production is a key process for studying photon interactions at high energies. Measurements of two-photon processes provide a direct access to the photon distribution function in protons and nuclei, and can probe the couplings between four vector bosons ($WW\gamma\gamma$) to find any deviation from the Standard Model. Two-photon measurements reported by the ATLAS Collaboration are presented. These measurments are performed using the proton-proton collisions at the centre-of-mass energy of 7~TeV ($pp \rightarrow pp\ell^+\ell^-$) and 8~TeV ($pp \rightarrow ppW^+W^- \rightarrow pp e^{\pm}\mu^{\mp}$), and using the lead-lead collisions at the centre-of-mass energy of 5.02~TeV (Pb~+~Pb~$\rightarrow$~Pb~+~Pb~+~$\mu^+\mu^-$).