Measurement of single top-quark production in association with a W boson in the single-lepton channel at √s = 8 TeV with the ATLAS detector

• Main Authors: Aad, Georges, Abbott, Brad, Abbott, Dale C, Abed Abud, Adam, Abeling, Kira, Abhayasinghe, Deshan Kavishka, Abidi, Syed Haider, AbouZeid, Ossama Sherif Alexander, Abraham, Nadine L, Abramowicz, Halina, Bjørke, Kristian, Bugge, Magnar Kopangen, Cameron, David Gordon, Catmore, James Richard, Garonne, Vincent, Gramstad, Eirik, Hellesund, Simen, Morisbak, Vanja, Oppen, Henrik, Ould-Saada, Farid, Pedersen, Maiken, Read, Alexander Lincoln, Rye, Eli Bæverfjord, Røhne, Ole Myren, Sandaker, Heidi, Vadla, Knut Oddvar Høie, Buanes, Trygve, Djuvsland, Julia Isabell, Eigen, Gerald, Fomin, Nikolai, Latour, Bertrand Pascal Christian, Lee, Graham Richard, Lipniacka, Anna, Stugu, Bjarne Sandvik, Træet, Are Sivertsen, Abreu, Henso, Abulaiti, Yiming, Acharya, Bobby S, Achkar, Baida, Adam, Lennart, Adam-Bourdarios, Claire, Adamczyk, Leszek, Adamek, Lukas, Adelman, Jareed, Adersberger, Michael, Adigüzel, Aytül, Adye, Tim, Affolder, Anthony Allen, Afik, Yoav, Agapopoulou, Christina, ATLAS, Collaboration
• Format: Article
• Language: English

The production cross-section of a top quark in association with a W boson is measured using proton–proton collisions at √s=8TeV. The dataset corresponds to an integrated luminosity of 20.2fb^−1, and was collected in 2012 by the ATLAS detector at the Large Hadron Collider at CERN. The analysis is performed in the single-lepton channel. Events are selected by requiring one isolated lepton (electron or muon) and at least three jets. A neural network is trained to separate the tW signal from the dominant tt¯ background. The cross-section is extracted from a binned profile maximum-likelihood fit to a two-dimensional discriminant built from the neural-network output and the invariant mass of the hadronically decaying W boson. The measured cross-section is σtW=26±7pb, in good agreement with the Standard Model expectation.