% IMPORTANT: The following is UTF-8 encoded. This means that in the presence % of non-ASCII characters, it will not work with BibTeX 0.99 or older. % Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or % “biber”. @ARTICLE{Aad:207440, author = {Aad, Georges and others}, title = {{O}bservation of {T}op-{Q}uark {P}air {P}roduction in {A}ssociation with a {P}hoton and {M}easurement of the $t\bar{t}\gamma$ {P}roduction {C}ross {S}ection in pp {C}ollisions at $\sqrt{s}=7$ {T}e{V} using the {ATLAS} {D}etector}, reportid = {PUBDB-2015-01348, CERN-PH-EP-2014-284. arXiv:1502.00586}, year = {2015}, note = {OA}, abstract = {A search is performed for top-quark pairs ($t\bar{t}$) produced together with a photon ($\gamma$) with transverse momentum $>20$ GeV using a sample of $t\bar{t}$ candidate events in final states with jets, missing transverse momentum, and one isolated electron or muon. The dataset 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 $t\bar{t}\gamma$ candidate events are observed in the electron and muon channels, to be compared to the expectation of $79\pm 26$ and $120\pm 39$ non-$t\bar{t}\gamma$ background events respectively. The production of $t\bar{t}\gamma$ events is observed with a significance of 5.3 standard deviations away from the null hypothesis. The $t\bar{t}\gamma$ 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 $\sigma_{t\bar{t}\gamma}^{fid} = 63 \pm 8 (stat.) ^{+17}_{-13} (syst.) \pm 1 (lumi.)$ fb per lepton flavor, in good agreement with the leading-order theoretical calculation normalized to the next-to-leading-order theoretical prediction of $48\pm 10$ fb.}, cin = {ATLAS}, 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)25 / PUB:(DE-HGF)15}, eprint = {1502.00586}, howpublished = {arXiv:1502.00586}, archivePrefix = {arXiv}, SLACcitation = {$\%\%CITATION$ = $arXiv:1502.00586;\%\%$}, url = {https://bib-pubdb1.desy.de/record/207440}, }