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

Abstract

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 𝐸𝛾 T >25 GeV. Jets are reconstructed in the rapidity range |𝑦jet| <4.4 and with a transverse momentum 𝑝jet T >20 GeV. The differential cross section 𝑑⁢σ/𝑑⁢𝐸𝛾 T 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 (η𝛾⁢𝑦jet ≥0) and opposite-sign (η𝛾⁢𝑦jet <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 𝐸𝛾 T ≲45 GeV, where the theoretical predictions overestimate the measured cross sections.