Search for direct top squark pair production in the single lepton final state at $\sqrt{s}=13~\mathrm{TeV}$

A search for direct top squark pair production in pp collisions at $\sqrt{s}=13~\mathrm{TeV}$ is presented. The data correspond to an integrated luminosity of $2.3~\mathrm{fb}^{-1}$ collected with the CMS detector during Run 2 of the LHC. The search is performed using events with a single isolated charged lepton (electron or muon), jets, and large imbalance in the measured transverse momentum. No significant excess in data is observed above the expectation from standard model processes. Exclusion limits are set in the context of supersymmetric models with pair production of top squarks that decay either to a top quark and a neutralino or to a bottom quark and a chargino. A scenario with nearly mass-degenerate chargino and neutralino is also considered for different values of the branching ratio of the top squark to a bottom quark and chargino.