Boosting vector leptoquark searches with boosted tops

Abstract

At the LHC, a TeV-scale leptoquark (LQ) that decays dominantly to a top quark ($t$) and a light charged lepton ($\ell=e,\mu$) would form a resonance system of \emph{boosted-$t$ $+$ high-$p_{\rm T}$-$\ell$}. We consider all possible vector LQ models within the Buchm\"{u}ller-R\"{u}ckl-Wyler classifications with the desired decay. We propose simple phenomenological Lagrangians that are suitable for bottom-up/experimental studies and, at the same time, can cover the relevant parameter spaces of these models. In this simplified framework, we study the pair and single production channels of vector LQs at the LHC. Interestingly, we find that, like the pair production, the cross sections of some single production processes also depend on the parameter $\kappa$ that appears in the gluon-vector LQ coupling. We adopt a search strategy of selecting events with at least one boosted hadronic top quark and exactly two high-$p_{\rm T}$ leptons of the same flavor and opposite sign. This combines events from the pair and single production processes and, therefore, can enhance the discovery potential beyond that of the pair-production-only searches. For $5\sigma$ discovery we find that vector LQs can be probed up to $2.55$ TeV for $100\%$ branching ratio in the $t\ell $ decay mode and $\mathcal{O}(1)$ new couplings at the $14$ TeV LHC with $3$ ab$^{-1}$ of integrated luminosity.