Measurement of the cross-section for producing a W boson in association with a single top quark in pp collisions at s = 13 √s=13 TeV with ATLAS

The inclusive cross-section for the associated production of a W boson and top quark is measured using data from proton-proton collisions at √s=13 TeV. The dataset corresponds to an integrated luminosity of 3.2 fb⁻¹, and was collected in 2015 by the ATLAS detector at the Large Hadron Collider at CERN. Events are selected requiring two opposite sign isolated leptons and at least one jet; they are separated into signal and control regions based on their jet multiplicity and the number of jets that are identified as containing b hadrons. The $Wt$ signal is then separated from the tt̄ background using boosted decision tree discriminants in two regions. The cross-section is extracted by fitting templates to the data distributions, and is measured to be 94 ± 10 (stat.)⁺²⁸₋₂₂ (syst.) ± 2 (lumi.) pb. The measurement is in agreement with the Standard Model prediction of σtheory = 71.7 ± 1.8\,(scale)\,± 3.4\,(PDF)\,pb.