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

Abstract

The production cross-section of a top quark in association with a W boson is measured using proton–proton collisions at √ s = 8 TeV. The dataset corresponds to an integrated luminosity of 20.2 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 ¯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 crosssection is σtW = 26 ± 7 pb, in good agreement with the Standard Model expectation.