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 $\sqrt{s}=7\mathrm{TeV}$ is presented. Photons are reconstructed in the pseudorapidity range $|{\eta }^{\gamma }|<1.37$ and with a transverse energy $E_{\mathrm{T}}^{\gamma }>25\mathrm{GeV}$. Jets are reconstructed in the rapidity range $|y^{\mathrm{jet}}|<4.4$ and with a transverse momentum $p_{\mathrm{T}}^{\mathrm{jet}}>20\mathrm{GeV}$. The differential cross section $d\sigma /d{E}_{\mathrm{T}}^{\gamma }$ is measured, as a function of the photon transverse energy, for three different rapidity ranges of the leading-$p_{\mathrm{T}}$ jet: $|y^{\mathrm{jet}}|<1.2$, $1.2\le |y^{\mathrm{jet}}|<2.8$ and $2.8\le |y^{\mathrm{jet}}|<4.4$. For each rapidity configuration the same-sign $({\eta }^{\gamma }{y}^{\mathrm{jet}}\ge 0)$ and opposite-sign $({\eta }^{\gamma }{y}^{\mathrm{jet}}<0)$ cases are studied separately. The results are based on an integrated luminosity of $37{\mathrm{pb}}^{-1}$, 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 $E_{\mathrm{T}}^{\gamma }\lesssim 45\mathrm{GeV}$, where the theoretical predictions overestimate the measured cross sections.

• Received 14 March 2012

DOI:https://doi.org/10.1103/PhysRevD.85.092014

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© 2012 CERN, for the ATLAS Collaboration