Boosted Top Tagging through Flavour-violating interactions at the LHC

Abstract

This paper describes a method for detecting a rare top quark decay into a charm quark and a Higgs boson (H), which decays further into b quarks, at the Large Hadron Collider (LHC), and introduces a tagging algorithm to identify boosted tops using large-R jets containing b- and c-tagged elements. We consider the associated production of the top quark with a W-boson and identify different observables to discriminate the signal from the Standard Model (SM) background events. Although our model with improved jet substructure methods outperforms existing approaches to tag such rare decay tops, the improvement in the New Physics reach in terms of $t \to cH$ branching ratio is marginal, even at the high luminosity run of LHC, compared to the existing limits from the LHC 13 TeV data. Although the result seems negative from the point of view of BSM reach, it is significant enough to motivate further studies in the search for the rare top decays at future colliders with higher energy and luminosity. Additionally, the paper utilizes SHAP, a Game Theory-based method, to analyze the contribution of each observable to the classification of events, offering valuable insights into the classifier. The approach presented in this paper is robust in scope and can be effectively implemented for similar probes of physics beyond the SM.