Leptoquarks decaying to a top quark and a charged lepton at hadron colliders

We study the sensitivity of the Tevatron and the 7 TeV LHC to a leptoquark $S$ coupling to a top quark and a charged lepton $L$ ($=e$, $\ensuremath{\mu}$, or $\ensuremath{\tau}$). For the Tevatron, we focus on the case ${m}_{S}<{m}_{t}$, where the leptoquark pair production cross section is large, and the decay is three-body: $S\ensuremath{\rightarrow}Wb{L}^{\ifmmode\pm\else\textpm\fi{}}$. We argue that existing Tevatron observations could exclude ${m}_{S}\ensuremath{\lesssim}160\text{ }\text{ }\mathrm{GeV}$. For ${m}_{S}>{m}_{t}$, we show that the LHC experiments with low integrated luminosity could be sensitive to such leptoquarks decaying to $t{l}^{\ifmmode\pm\else\textpm\fi{}}$ with $l=\ensuremath{\mu}$ or $\ensuremath{\tau}$.