Search for top-squark pair production in final states with one lepton, jets, and missing transverse momentum using 36 fb −1 of √s =13 TeV pp collision data with the ATLAS detector

CERN-LHC. The results of a search for the direct pair production of stops, the supersymmetric partner of the top-quark, in final states with one isolated electron or muon, several energetic jets, and missing transverse momentum are reported. The search uses data from pp collisions delivered by the Large Hadron Collider in 2015 and 2016 at a center-of-mass energy of 13 TeV and recorded by the ATLAS detector, corresponding to an integrated luminosity of 36.1/fb. A wide range of signal scenarios with different mass splittings between the stop, the lightest neutralino and possible intermediate gauginos or higgsinos is considered, including cases where the W-bosons or the top-quarks are off-shell. The analysis also targets the production of dark matter in association with a pair of top-quarks using the same final state. No significant excess over the Standard Model prediction is observed. The null results are used to set exclusion limits at 95% confidence level in several benchmark models, which reach up to a stop mass of 940 GeV. Stringent exclusion limits are also derived for all other considered stop decay scenarios, and upper limits are set on the visible cross-section for processes beyond the Standard Model.