Hunting for scalar leptoquarks with boosted tops and light leptons

The LHC search strategies for leptoquarks that couple dominantly to a top quark are different than for the ones that couple mostly to the light quarks. We consider charge 1/3 (phi(1)) and 5/3 (phi(5)) scalar leptoquarks that can decay to a top quark and a charged lepton (tl) giving rise to a resonance system of a boosted top and a high-p(T) lepton. We introduce simple phenomenological models suitable for bottom-up studies and explicitly map them to all possible scalar leptoquark models within the Buchmuller-Ruckl-Wyler classifications that can have the desired decays. We study pair and single productions of these leptoquarks. Contrary to the common perception, we find that the single production of top-philic leptoquarks phi = {phi(1), phi(5)} in association with a lepton and jets could be significant for order one phi tl coupling in certain scenarios. We propose a strategy of selecting events with at least one hadronic-top and two high-p(T) same flavor opposite sign leptons. This captures events from both pair and single productions. Our strategy can significantly enhance the LHC discovery potential especially in the high-mass region where single productions become more prominent. Our estimation shows that a scalar leptoquark as heavy as similar to 1.7 TeV can be discovered at the 14 TeV LHC with 3 ab(-1) of integrated luminosity in the tll + X channel for 100% branching ratio in the phi -> tl decay mode. However, in some scenarios, the discovery reach can increase beyond 2 TeV even though the branching ratio comes down to about 50%.