Measurement of single top-quark production in association with a W boson in the single-lepton channel at $\sqrt{s}=8\phantom{\rule{0.166667em}{0ex}}\text{TeV}$ with the ATLAS detector

The production cross-section of a top quark in association with a W boson is measured using proton–proton collisions at $\sqrt{s}=8\phantom{\rule{0.166667em}{0ex}}\text{TeV}$ . The dataset corresponds to an integrated luminosity of $20.2\phantom{\rule{0.166667em}{0ex}}{\text{fb}}^{-1}$ , 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 $t\overline{t}$ 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 ${\sigma }_{\mathrm{tW}}=26±7\phantom{\rule{0.166667em}{0ex}}\text{pb}$ , in good agreement with the Standard Model expectation.