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???) is presented, with a significance of 6.6 standard deviations (?). 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 3.2?. 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 ?t¯tHB??=1.56+0.34?0.32?fb, which is compatible with the standard model prediction of 1.13+0.08?0.11?fb. The fractional contribution of the CP-odd component is measured to be fHttCP=0.00±0.33.

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