Optimized probes of CP-odd effects in the tt¯h process at hadron colliders

Abstract

We use machine learning (ML) and non-ML techniques to study optimized CP-odd observables, directly and maximally sensitive to the CP-odd iκ˜t¯γ5th interaction at the LHC and prospective future hadron colliders using the final state with a Higgs boson and a top quark pair, pp→tt¯h, followed by semileptonic t decays. We perform phase-space optimization of manifestly CP-odd observables (ω), sensitive to the sign of κ˜, and constructed from experimentally accessible final state momenta. We identify a simple optimized linear combination α⋅ω that gives similar sensitivity as the studied fully fledged ML models. Using α⋅ω we project the expected sensitivities to κ˜ at HL-LHC, HE-LHC, and FCC-hh.