Measurement of the production cross section of an isolated photon associated with jets in proton-proton collisions at √s= 7 TeV with the ATLAS detector

A measurement of the cross section for the production of an isolated photon in association with jets in proton-proton collisions at a center-of-mass energy pffisffiffi ¼ 7 TeV is presented. Photons are reconstructed in the pseudorapidity range jj < 1:37 and with a transverse energy E T > 25 GeV. Jets are reconstructed in the rapidity range jyjetj < 4:4 and with a transverse momentum pjetT > 20 GeV. The differential cross section d=dET is measured, as a function of the photon transverse energy, for three different rapidity ranges of the leading-pT jet: jyjetj < 1:2, 1:2 jyjetj < 2:8 and 2:8 jyjetj < 4:4. For each rapidity configuration the same-sign ðyjet 0Þ and opposite-sign ðyjet < 0Þ cases are studied separately. The results are based on an integrated luminosity of 37 pb1, collected with the ATLAS detector at the LHC. Next-to-leading order perturbative QCD calculations are found to be in fair agreement with the data, except for ET & 45 GeV, where the theoretical predictions overestimate the measured cross sections.