Search for top squarks in final states with one isolated lepton in $\sqrt{s}$ = 13 TeV pp collisions with the ATLAS detector

The result of a search for the direct pair production of top squarks, the supersymmetric partner of the top-quark, in final states with one isolated electron or muon, jets, and missing transverse momentum is reported. The search uses data from $pp$ collisions recorded at the LHC with the ATLAS detector at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV correspoinding to an integrated luminosity of 36 $\mathrm{fb}^{-1}$. Dedicated analysis for the Higgsino LSP model is performed considering small mass splitting between electroweakinos and the realistic branching ratio of a top squark. No significant excess over the Standard Model predictions is observed. Exclusion limits at 95\% confidence level in the Higgsino LSP model are set. The top squark mass is excluded up to 810 GeV for 2 GeV mass splitting between the chargino and the lightest neutralino. The results are also reinterpreted to set exclusion limits in a Bino-Higgsino mixed LSP model.