@article{88e249af04dc4d878c15a3ba41014eaa,
title = "Observation of top-quark pair production in association with a photon and measurement of the t t ¯ γ production cross section in pp collisions at √s =7 TeV using the ATLAS detector",
abstract = "A search is performed for top-quark pairs (tt¯) produced together with a photon (γ) with transverse energy greater than 20 GeV using a sample of tt¯ 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 4.59 fb-1 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 tt¯γ candidate events are observed in the electron and muon channels, to be compared to the expectation of 79±26 and 120±39 non-tt¯γ background events, respectively. The production of tt¯γ events is observed with a significance of 5.3 standard deviations away from the null hypothesis. The tt¯γ 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 σtt¯γfid×BR=63±8(stat)-13+17(syst)±1(lumi) fb per lepton flavor, in good agreement with the leading-order theoretical calculation normalized to the next-to-leading-order theoretical prediction of 48±10 fb.",
author = "{Atlas Collaboration} and G. Aad and B. Abbott and J. Abdallah and {Abdel Khalek}, S. and O. Abdinov and R. Aben and B. Abi and M. Abolins and Abouzeid, {O. S.} and H. Abramowicz and H. Abreu and R. Abreu and Y. Abulaiti and Acharya, {B. S.} and L. Adamczyk and Adams, {D. L.} and J. Adelman and S. Adomeit and T. Adye and T. Agatonovic-Jovin and Aguilar-Saavedra, {J. A.} and M. Agustoni and Ahlen, {S. P.} and F. Ahmadov and G. Aielli and H. Akerstedt and {\AA}kesson, {T. P.A.} and G. Akimoto and Akimov, {A. V.} and Alberghi, {G. L.} and J. Albert and S. Albrand and {Alconada Verzini}, {M. J.} and M. Aleksa and Aleksandrov, {I. N.} and C. Alexa and G. Alexander and G. Alexandre and T. Alexopoulos and M. Alhroob and G. Alimonti and L. Alio and J. Alison and Allbrooke, {B. M.M.} and Allison, {L. J.} and Allport, {P. P.} and J. Almond and A. Aloisio and A. Alonso and Rudolph, {M. S.}",
note = "Publisher Copyright: {\textcopyright} 2015 CERN. {\textcopyright} 2015 CERN, for the ATLAS Collaboration. Published by the American Physical Society under the terms of the »http://creativecommons.org/licenses/by/3.0/» Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.",
year = "2015",
month = apr,
day = "28",
doi = "10.1103/PhysRevD.91.072007",
language = "English (US)",
volume = "91",
journal = "Physical Review D - Particles, Fields, Gravitation and Cosmology",
issn = "1550-7998",
publisher = "American Physical Society",
number = "7",
}