Search for direct top squark pair production in the 3-body decay mode with one-lepton final states in $\sqrt{s}$=13 TeV $\mathit{pp}$ collisions with the ATLAS detector

Natural supersymmetry suggests a light top squark, possibly within the discovery reach of Run-2 of the LHC. This proceedings presents the latest result of an analysis targeting a compressed region of the top squark phase space where the mass difference between the top squark and the lightest neutralino is smaller than the top-quark mass, using $pp$ collision data collected over the full Run-2 of the LHC. A machine learning technique was employed in the analysis to improve the discrimination of signals from backgrounds dominated by the $t\bar{t}$ process. No significant deviation from the predicted Standard Model background is observed, and limits at 95% confidence level on the supersymmetric benchmark model are set, excluding top squark masses up to 720 GeV with neutralino masses up to 580 GeV.