Measurement of isolated-photon pair production in pp collisions at root s=7 TeV with the ATLAS detector

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 root s = 7 TeV. 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 (vertical bar eta vertical bar < 1.37 and 1.52 < vertical bar eta vertical bar 2.37) and with an angular separation Delta R > 0.4, is 44.0(-4.2)(+3.2) 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.
Bibliographic reference
ATLAS Collaboration Cabrera Urbán, Susana Castillo Giménez, María Victoria Costa Mezquita, María José Fassi, Farida Ferrer Soria, Antonio Fiorini, Luca Fuster Verdú, Juan A. García García, Carmen García Navarro, José Enrique González de la Hoz, Santiago Hernández Jiménez, Yesenia Higón Rodríguez, Emilio Irles Quiles, Adrián Kaci, Mohammed Lacasta Llácer, Carlos Lacuesta Miquel, Vicente March Ruiz, Luis Martí García, Salvador Miñano Moya, Mercedes Mitsou, Vasiliki Moles Valls, Regina Moreno Llácer, María Oliver García, Elena Pedraza López, Sebastián Pérez García-Estañ, María Teresa Romero Adam, E. Ros Martínez, Eduardo Salt Cairols, José Sánchez Martínez, V. Soldevila, U. Sánchez, J. Torró Pastor, Emma Valero Biot, Alberto Valladolid Gallego, E. Valls Ferrer, Juan Antonio Villaplana Pérez, Miguel Vos, Marcel 2013 Measurement of isolated-photon pair production in pp collisions at root s=7 TeV with the ATLAS detector Journal of High Energy Physics 01 1 086-1 086-42