Direct Higgs-top CP-phase measurement with $$ t\overline{t}h $$ at the 14 TeV LHC and 100 TeV FCC

Abstract

Abstract The study of the Higgs boson’s properties is a cornerstone of the LHC and future collider programs. In this paper, we examine the potential to directly probe the Higgs-top interaction strength and CP-structure in the $$ t\overline{t}h $$ t t ¯ h channel with the Higgs boson decaying to bottom-quark pairs and top-quarks in the di-leptonic mode. We adopt the BDRS algorithm to tag the boosted Higgs and exploit the M2-assisted reconstruction to compute observables sensitive to the CP-phase at the $$ t\overline{t} $$ t t ¯ rest frame, where the new physics sensitivity can be enhanced. Performing a side-band analysis at the LHC to control the continuum $$ t\overline{t}b\overline{b} $$ t t ¯ b b ¯ background, we find that the Higgs-top strength and CP-phase can be probed up to $$ {\delta}_{\kappa_t} $$ δ κ t ≲ 20% and |α| ≲ 36° at 95% CL, respectively. We also derive that a similar analysis at a 100 TeV future collider could further improve the precision to $$ {\delta}_{\kappa_t} $$ δ κ t ≲ 1% and |α| ≲ 1.5°, where the CP-odd observables play a crucial role, boosting the sensitivity on the CP-phase.