Search for third-generation scalar leptoquarks decaying to a top quark and a $$\tau $$ lepton at $$\sqrt{s}=13\,\text {Te}\text {V} $$s=13Te

A search for pair production of heavy scalar leptoquarks (LQs), each 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 that decayed to hadrons, and additional jets. The data were collected in 2016 in proton–proton collisions at $$\sqrt{s}=13\,\text {Te}\text {V} $$ with the CMS detector at the LHC, and correspond to an integrated luminosity of 35.9 $$\,\text {fb}^{-1}$$ . No evidence for pair production of LQs is found. Assuming a branching fraction of unity for the decay $$\mathrm {LQ} \rightarrow \mathrm {t}\tau $$ , upper limits on the production cross section are set as a function of LQ mass, excluding masses below 900 $$\,\text {Ge}\text {V}$$ at 95% confidence level. These results provide the most stringent limits to date on the production of scalar LQs that decay to a top quark and a $$\tau $$ lepton.