Probing the CP nature of the top-Higgs Yukawa coupling in tt¯H and tH events with H→bb¯ decays using the ATLAS detector at the LHC

The CP properties of the coupling between the Higgs boson and the top quark are investigated with 139 fb−1 of proton-proton collision data recorded by the ATLAS experiment at the LHC at a centre-of-mass energy of s√=13 TeV. The CP structure of the top quark-Higgs boson Yukawa coupling is probed in events with a Higgs boson decaying into a pair of b-quarks and produced in association with either a pair of top quarks, tt¯H, or a single top quark, tH. Events containing one or two electrons or muons are used for the measurement. In an extension of the Standard Model with a CP-odd admixture to the top-Higgs Yukawa coupling, the mixing angle between CP-even and CP-odd couplings is measured to be α=11∘+52∘−73∘.