Observation of the Associated Production of a Single Top Quark and a W Boson in pp Collisions at √s = 8 TeV

Chatrchyan, S. and Khachatryan, V. and Sirunyan, A. M. and Tumasyan, A. and Adam, W. and Bergauer, T. and Dragicevic, M. and Erö, J. and Fabjan, C. and Friedl, M. and Frühwirth, R. and Ghete, V. M. and Hartl, C. and Hörmann, N. and Hrubec, J. and Jeitler, M. and Kiesenhofer, W. and Knünz, V. and Krammer, M. and Krätschmer, I. and Liko, D. and Mikulec, I. and Rabady, D. and Rahbaran, B. and Rohringer, H. and Schöfbeck, R. and Strauss, J. and Taurok, A. and Treberer-Treberspurg, W. and Waltenberger, W. and Bencze, György and Hajdu, Csaba and Hidas, Pál and Horváth, Dezső and Siklér, Ferenc and Veszprémi, Viktor and Vesztergombi, György and Zsigmond, Anna Júlia and Béni, Noémi Tekla and Molnár, József and Pálinkás, József and Szillási, Zoltán and Karancsi, János and Raics, Péter and Trócsányi, Zoltán and Ujvári, Balázs and Veres, Gábor (2014) Observation of the Associated Production of a Single Top Quark and a W Boson in pp Collisions at √s = 8 TeV. PHYSICAL REVIEW LETTERS, 112 (23). ISSN 0031-9007

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Abstract

The first observation of the associated production of a single top quark and a W boson is presented. The analysis is based on a data set corresponding to an integrated lu- minosity of 12.2 fb−1 of proton-proton collisions at √s = 8 TeV recorded by the CMS experiment at the LHC. Events with two leptons and a jet originating from a b quark are selected. A multivariate analysis based on kinematic and topological properties is used to separate the signal from the dominant tt background. An excess consistent with the signal hypothesis is observed, with a significance which corresponds to 6.1 standard deviations above a background-only hypothesis. The measured production cross section is 23.4 ± 5.4 pb, in agreement with the standard model prediction.

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