A measurement of the production cross section for two isolated photons in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=8\mathrm{TeV}$ is presented. The results are based on an integrated luminosity of $20.2{\mathrm{fb}}^{-1}$ recorded by the ATLAS detector at the Large Hadron Collider. The measurement considers photons with pseudorapidities satisfying $|{\eta }^{\gamma }|<1.37$ or $1.56<|{\eta }^{\gamma }|<2.37$ and transverse energies of respectively $E_{\mathrm{T},1}^{\gamma }>40\mathrm{GeV}$ and $E_{\mathrm{T},2}^{\gamma }>30\mathrm{GeV}$ for the two leading photons ordered in transverse energy produced in the interaction. The background due to hadronic jets and electrons is subtracted using data-driven techniques. The fiducial cross sections are corrected for detector effects and measured differentially as a function of six kinematic observables. The measured cross section integrated within the fiducial volume is $16.8\pm 0.8\mathrm{pb}$. The data are compared to fixed-order QCD calculations at next-to-leading-order and next-to-next-to-leading-order accuracy as well as next-to-leading-order computations including resummation of initial-state gluon radiation at next-to-next-to-leading logarithm or matched to a parton shower, with relative uncertainties varying from 5% to 20%.

• Received 13 April 2017

DOI:https://doi.org/10.1103/PhysRevD.95.112005

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© 2017 CERN, for the ATLAS Collaboration