Search for singly produced third-generation leptoquarks decaying to a $\tau$ lepton and a b quark in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$

A search is presented for singly produced third-generation scalar leptoquarks decaying to a $\tau$ lepton and a b quark. Events containing two $\tau$ leptons and one jet originating from a b quark are considered. The search is based on proton-proton collision data at a center-of-mass energy of $13~\mathrm{TeV}$ recorded with the CMS detector and corresponding to an integrated luminosity of $35.9~\mathrm{fb}^{-1}$. Upper limits are set on the third-generation scalar leptoquark production cross section as a function of the leptoquark mass. Results are compared with theoretical predictions to obtain lower limits on the leptoquark mass. At $95\%$ confidence level, third-generation scalar leptoquarks decaying to a $\tau$ lepton and a b quark with unit coupling are excluded for masses below 744 GeV. Limits are also set on the couplings of such leptoquarks as a function of their mass.