Search for third generation scalar leptoquarks decaying to a top quark and a tau lepton at sqrt(s) = 13 TeV

A search for pair production of heavy scalar leptoquarks (LQs) decaying into a top quark and a $\tau$ lepton is presented. The search considers final states with an electron or a muon, one or two $\tau$ leptons decaying to hadrons, and additional jets. The data collected in proton-proton collisions in 2016 at ${\sqrt{s}=13}~\mathrm{TeV}$ with the CMS detector at the LHC, corresponding to an integrated luminosity of $35.9~\mathrm{fb}^{-1}$ are used. No evidence for pair production of leptoquarks is found. Upper limits on the production cross section are set as a function of LQ mass, assuming a branching fraction of unity for the decay $\mathrm{LQ}\to \mathrm{t} \tau$, excluding masses below $900~\mathrm{GeV}$ at $95\%$ confidence level. These results provide the most stringent exclusion limits on the production of scalar leptoquarks in the top quark and $\tau$ lepton decay channel to date.