Photon identification with the ATLAS detector

Good photon identification capabilities are important for many aspects of the ATLAS physics program at the LHC, from Higgs boson measurements to new physics searches. The identification of prompt photons and the rejection of background coming mostly from photons in hadron decays relies on the high granularity of the ATLAS calorimeter. Several data-driven methods are used to measure the efficiency of the photon identification requirements, covering a broad energy spectrum. At low energies, photons from radiative $Z$ boson decays are used. In the medium energy range, similarities between electron and photon showers are exploited using $Z \rightarrow ee$ decays. At high energies, inclusive photon samples are used. The results of these measurements performed in proton-proton collisions data at a center-of-mass energy of $\sqrt{s} = 13$ TeV taken in 2015 and 2016 corresponding to an integrated luminosity of $\mathcal{L}$ = 36.1 fb$^{-1}$ in the case of the radiative $Z$ boson and electron extrapolation method and $\mathcal{L}$ = 37.1 fb$^{-1}$ for the matrix method are presented.