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 W t signal is then separated from the tt¯ 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 σW t = 94±10 (stat.)−22 +28 (syst.)±2 (lumi.) pb. The measured value is in good agreement with the SM prediction of σtheory = 71.7±1.8 (scale)± 3.4.
Bibliographical note24 pages in total, author list starting page 25, 6 figures, 4 tables, submitted to JHEP, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2015-16/