Boosting the Direct CP Measurement of the Higgs-Top Coupling

Abstract: Characterizing the 125 GeV Higgs is a critical component of the physics program at the LHC Run II. In this Letter, we consider $t\bar{t}H$ associated production in the dileptonic mode. We demonstrate that the difference in azimuthal angle between the leptons from top decays can directly reveal the CP-structure of the top-Higgs coupling with the sensitivity of the measurement substantiality enhanced in the boosted Higgs regime. We first show how to access this channel via $H \to b\bar{b}$ jet-substructure tagging, then demonstrate the ability of the new variable to measure CP. Our analysis includes all signal and background samples simulated via the MC@NLO algorithm including hadronization and underlying-event effects. Using boosted Higgs substructure with dileptonic tops, we find that the top-Higgs coupling strength and the CP structure can be directly probed with achievable luminosity at the 13 TeV LHC.