A Measurement of the Production Cross Section of a Single Top Quark in Association with a $W$-boson at $\sqrt{s} = 13$ TeV with the ATLAS Detector at the Large Hadron Collider

A measurement of the Standard Model cross section for the production of a single top quark in association with a $W$-boson from proton-proton collisions is presented. Collision data at a center-of-mass energy of 13 TeV totaling 139 inverse femtobarns collected by the ATLAS detector on the Large Hadron Collider is used to study the process. Binary classifiers trained using kinematic properties of observable particles are used to separate the signal process from a large top pair production background. A binned maximum likelihood fit is performed to extract the Standard Model cross section for the signal process, along with a secondary top pair cross section measurement and uncertainties related to object reconstruction with the detector and theoretical models. The measured cross section is the most precise measurement performed using the ATLAS detector and is in good agreement with the Standard Model prediction.