Search for leptoquarks coupled to third-generation quarks in proton-proton collisions at $\sqrt{s}=$ 13 TeV
Phys.Rev.Lett. 121 (2018) 241802
The collaboration

Abstract (data abstract)
Three of the most significant measured deviations from standard model predictions, the enhanced decay rate for $\mathrm{B}\to\mathrm{D}^{\ast}\tau\nu$, hints of lepton universality violation in $\mathrm{B}\to\mathrm{K}^{\ast}\ell\ell$ decays, and the anomalous magnetic moment of the muon, can be explained by the existence of leptoquarks (LQs) with large couplings to third-generation quarks and masses at the TeV scale. The existence of these states can be probed at the LHC in high energy proton-proton collisions. A novel search is presented for pair production of LQs coupled to a top quark and a muon using data at a center-of-mass energy of $13\,\mathrm{TeV}$, corresponding to an integrated luminosity of $35.9\,\mathrm{fb}^{-1}$, recorded by the CMS experiment. No deviation from the standard model prediction has been observed and scalar LQs decaying exclusively into $t\mu$ are excluded up to masses of $1420\,\mathrm{GeV}$. The results of this search are combined with those from previous searches for LQ decays into $t\tau$ and $b\nu$, which excluded scalar LQs below masses of $900$ and $1080\,\mathrm{GeV}$. Vector LQs are excluded up to masses of $1190\,\mathrm{GeV}$ for all possible combinations of branching fractions to $t\mu$, $t\tau$ and $b\nu$. With this analysis, all relevant couplings of LQs with an electric charge of $-1/3$ to third-generation quarks are probed for the first time.