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 √s = 7  TeV is presented. Photons are reconstructed in the pseudorapidity range |ηγ|<1.37 and with a transverse energy ETγ>25  GeV. Jets are reconstructed in the rapidity range |yjet|<4.4 and with a transverse momentum pTjet>20  GeV. The differential cross section dσ/dETγ is measured, as a function of the photon transverse energy, for three different rapidity ranges of the leading-pT jet: |yjet|<1.2, 1.2≤|yjet|<2.8 and 2.8≤|yjet|<4.4. For each rapidity configuration the same-sign (ηγyjet≥0) and opposite-sign (ηγyjet<0) cases are studied separately. The results are based on an integrated luminosity of 37  pb-1, 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 ETγ≲45  GeV, where the theoretical predictions overestimate the measured cross sections.