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Evidence for the associated production of a W boson and a top quark in ATLAS at √s=7 TeV

CollaborationWith : Abdelalim Aly, Ahmed Aly / Alexandre, Gauthier / Backes, Moritz / Barone, Gaetano / Bell, Paul / Bell, William / Benhar Noccioli, Eleonora / Blondel, Alain / Bucci, Francesca / Clark, Allan Geoffrey / Dao, Valerio / Doglioni, Caterina / Ferrere, Didier / Gadomski, Szymon / Gonzalez Sevilla, Sergio / Goulette, Marc / Iacobucci, Giuseppe / La Rosa, Alessandro / Lister, Alison / Martin Dit Latour, Bertrand / Mermod, Philippe / Mora Herrera, Maria Clemencia Rosario / Nektarijevic, Snezana / Nikolics, Katalin / Pasztor, Arpad / Picazio, Attilio / Pohl, Martin / Rosbach, Kilian / Rosselet, Laurent / Wu, Xin
Published in Physics Letters. B. 2012, vol. 716, no. 1, p. 142-159
Abstract This Letter presents evidence for the associated production of a W boson and a top quark using 2.05 fb−1 of pp collision data at √s = 7 TeV accumulated with the ATLAS detector at the LHC. The analysis is based on the selection of the dileptonic final states with events featuring two isolated leptons, electron or muon, with significant transverse missing momentum and at least one jet. An approach based on boosted decision trees has been developed to improve the discrimination of single top-quark Wt events from background. A template fit to the final classifier distributions is performed to determine the crosssection. The result is incompatible with the background-only hypothesis at the 3.3σ level, the expected sensitivity assuming the Standard Model production rate being 3.4σ. The corresponding cross-section is determined and found to be σWt = 16.8±2.9 (stat)±4.9 (syst) pb, in good agreement with the Standard Model expectation. From this result the CKM matrix element |Vtb| = 1.03+0.16 −0.19 is derived assuming that the Wt production through |Vts| and |Vtd| is small
Keywords ATLASTop quarkW+tSingle top-quark
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ATLAS COLLABORATION. Evidence for the associated production of a W boson and a top quark in ATLAS at √s=7 TeV. In: Physics Letters. B, 2012, vol. 716, n° 1, p. 142-159. doi: 10.1016/j.physletb.2012.08.011 https://archive-ouverte.unige.ch/unige:39886

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Deposited on : 2014-09-01

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