Abstract
A search is performed for top-quark pairs () produced together with a photon () with transverse energy greater than 20 GeV using a sample of candidate events in final states with jets, missing transverse momentum, and one isolated electron or muon. The data set used corresponds to an integrated luminosity of of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. In total, 140 and 222 candidate events are observed in the electron and muon channels, to be compared to the expectation of and non- background events, respectively. The production of events is observed with a significance of 5.3 standard deviations away from the null hypothesis. The production cross section times the branching ratio (BR) of the single-lepton decay channel is measured in a fiducial kinematic region within the ATLAS acceptance. The measured value is per lepton flavor, in good agreement with the leading-order theoretical calculation normalized to the next-to-leading-order theoretical prediction of .
- Received 3 February 2015
DOI:https://doi.org/10.1103/PhysRevD.91.072007
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© 2015 CERN, for the ATLAS Collaboration