Measurement of photon and photon+jet production cross sections at 7 TeV and constraints to PDFs

The inclusive isolated-photon production and the dynamics of isolated-photon plus jet production in pp collisions at a centre-of-mass energy of 7 TeV has been studied with the ATLAS detector at the LHC using an integrated luminosity of 4.5 fb−1 and 37 pb−1, respectively. Measurements of the inclusive isolated-photon cross sections are presented as a function of the photon transverse energy and the impact of the measurements to constraint the gluon PDF is evaluated. Measurements of the isolated-photon plus jet differential cross sections are presented as functions of the photon transverse energy, the jet transverse momentum, the jet rapidity, the difference in azimuthal angle between the photon and the jet, the photon-jet invariant mass and the scattering angle in the photon-jet centre-of-mass frame. Next-to-leading-order QCD calculations are compared to the measurements and provide a good description of the data in both analyses, except in the case of the azimuthal angle.