Measurement of photon production at ATLAS

The production of isolated prompt photons at hadron colliders provides stringent tests of perturbative QCD and can be used to evaluate probability distribution functions of partons in the proton. At the LHC, the ATLAS Collaboration has performed precise measurements of the inclusive production of isolated-prompt photons in proton-proton collisions at a centre-of-mass energy of 13~TeV. The ratio of the cross sections for inclusive isolated-photon production at centre-of-mass energies of 13 and 8~TeV has been measured as a function of the photon transverse energy in different regions of the photon pseudorapidity. The measurements are compared with state-of-the art theory predictions at next-to-leading as well as next-to-next-to-leading order in perturbative QCD in the case of the measurement of inclusive production of isolated-prompt photons.