Measurement of isolated-photon pair production in pp collisions at root s=7 TeV with the ATLAS detector
Buanes, Trygve; Burgess, Thomas; Eigen, Gerald; Kastanas, Alex; Liebig, Wolfgang; Lipniacka, Anna; Rosendahl, Peter Lundgaard; Sandaker, Heidi; Sjursen, Therese B.; Stugu, Bjarne Sandvik; Tonoyan, Arshak; Ugland, Maren; Bugge, Lars; Buran, Torleiv; Cameron, David Gordon; Czyczula, Zofia; Gjelsten, Børge Kile; Gramstad, Eirik; Lund, Esben; Ould-Saada, Farid; Pajchel, Katarina; Pylypchenko, Yuriy; Read, Alexander Lincoln; Røhne, Ole Myren; Samset, Bjørn Hallvard; Smestad, Lillian; Stapnes, Steinar; Strandlie, Are; Aad, Georges; Abajyan, Tatevik; Abbott, Brad; Abdallah, Jalal; Abdel Khalek, Samah; Abdelalim, Ahmed Ali; Abdesselam, Abdel; Abdinov, Ovsat Bahram oglu; Abi, Babak; Abolins, Maris; AbouZeid, Hass; Abramowicz, Halina; Abreu, Henso; Acerbi, Emilio; Adams, David; Addy, Tetteh N.; Adelman, Jareed; Adomeit, Stefanie; Adragna, Paolo; Adye, Tim; Aefsky, Scott Alan; Aharrouche, Mohamed; ATLAS, Collaboration
Peer reviewed, Journal article
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The ATLAS experiment at the LHC has measured the production cross section of events with two isolated photons in the final state, in proton-proton collisions at s√=7TeV. The full data set collected in 2011, corresponding to an integrated luminosity of 4.9 fb−1, is used. The amount of background, from hadronic jets and isolated electrons, is estimated with data-driven techniques and subtracted. The total cross section, for two isolated photons with transverse energies above 25 GeV and 22 GeV respectively, in the acceptance of the electromagnetic calorimeter (|η| < 1.37 and 1.52 < |η| < 2.37) and with an angular separation ΔR > 0.4, is 44.0+3.2−4.2 pb. The differential cross sections as a function of the di-photon invariant mass, transverse momentum, azimuthal separation, and cosine of the polar angle of the largest transverse energy photon in the Collins-Soper di-photon rest frame are also measured. The results are compared to the prediction of leading-order parton-shower and next-to-leading-order and next-to-next-to-leading-order parton-level generators.