Measurements of isolated photon pair production in association with jets in pp collisions at √s = 8 TeV with the ATLAS detector

Measurements of integrated and differential production cross section of two isolated photons in events with and without associated hadronic jets based on the 2012 dataset of 20.3 fb⁻¹ integrated luminosity of proton-proton collisions at √s=8 TeV collected by the ATLAS experiment are presented. The measurements consider photons with pseudorapidities of |η^γ|<1.37 or 1.56<|η^γ|<2.37 and transverse energy of ET^γ>22 GeV. Jets are required to have pTʲ>25 GeV for |ηʲ|<2.4 and pTʲ>50 GeV for 2.4<|ηʲ|<4.4. Events are classified into categories based on the number of jets and integrated fiducial cross sections of diphoton production in association with inclusive and exclusive number of jets are presented. Fiducial cross sections, differential in sixteen diphoton, jet, dijet and photon-jet observables, are presented and compared with leading-order Sherpa 1.4.1 predictions in all jet categories, fixed-order next-to-leading-order GoSam and BlackHat calculations in selected categories, and NLO-matched predictions from Sherpa 2.2.14 in all categories. Overall, the NLO predictions provide a reasonable description of the data, with significant discrepancies observed for increasing jet multiplicity, particularly for angular variables, attributable to the absence of higher-order terms in the calculations. The Sherpa 2.2.14 NLO-matched predictions provide the best overall description of the data across all jet categories and observables.