Measurements of tt¯H production and the CP structure of the Yukawa interaction between the higgs boson and top quark in the diphoton decay channel

Abstract

The first observation of the t¯tH process in a single Higgs boson decay channel with the full reconstruction of the final state (H → γγ) is presented, with a significance of 6.6 standard deviations (σ). The CP structure of Higgs boson couplings to fermions is measured, resulting in an exclusion of the pure CP-odd structure of the top Yukawa coupling at 3.2σ. The measurements are based on a sample of proton-proton collisions at a center-of-mass energy √ s = 13 TeV collected by the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb−1. The cross section times branching fraction of the t¯tH process is measured to be σt ¯ tHB γγ = 1.56 + 0.34 − 0.32 fb, which is compatible with the standard model prediction of 1.13þ0.08 −0.11 fb. The fractional contribution of the CP-odd component is measured to be fHtt CP = 0.00 ± 0.33 .