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@ARTICLE{Aad:221709,
      author       = {Aad, Georges and others},
      collaboration = {{ATLAS Collaboration}},
      title        = {{O}bservation of top-quark pair production in association
                      with a photon and measurement of the $t\bar{t}\gamma$
                      production cross section in pp collisions at $\sqrt{s}=7$
                      {T}e{V} using the {ATLAS} detector},
      journal      = {Physical review / D},
      volume       = {91},
      number       = {7},
      issn         = {1550-7998},
      publisher    = {American Physical Society},
      reportid     = {PUBDB-2015-02789, CERN-PH-EP-2014-284. arXiv:1502.00586},
      pages        = {072007},
      year         = {2015},
      note         = {OA},
      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.},
      keywords     = {p p: colliding beams (INSPIRE) / top: pair production
                      (INSPIRE) / photon: associated production (INSPIRE) / p p:
                      scattering (INSPIRE) / transverse momentum: missing-energy
                      (INSPIRE) / higher-order: 1 (INSPIRE) / higher-order: 0
                      (INSPIRE) / ATLAS (INSPIRE) / final state: ((n)jet lepton)
                      (INSPIRE) / cross section: measured (INSPIRE) / top:
                      branching ratio (INSPIRE) / CERN LHC Coll (INSPIRE) /
                      acceptance (INSPIRE) / kinematics (INSPIRE) / background
                      (INSPIRE) / experimental results (INSPIRE) / p p --> 2top
                      photon anything (INSPIRE) / 7000 GeV-cms (INSPIRE)},
      cin          = {ATLAS},
      ddc          = {530},
      cid          = {I:(DE-H253)ATLAS-20120731},
      pnm          = {611 - Fundamental Particles and Forces (POF3-611)},
      pid          = {G:(DE-HGF)POF3-611},
      experiment   = {EXP:(DE-H253)LHC-Exp-ATLAS-20150101},
      typ          = {PUB:(DE-HGF)16 / PUB:(DE-HGF)15},
      eprint       = {1502.00586},
      howpublished = {arXiv:1502.00586},
      archivePrefix = {arXiv},
      SLACcitation = {$\%\%CITATION$ = $arXiv:1502.00586;\%\%$},
      doi          = {10.1103/PhysRevD.91.072007},
      url          = {https://bib-pubdb1.desy.de/record/221709},
}