Determining the relative size of the CP-even and CP-odd Higgs boson couplings to a fermion at the LHC

We demonstrate that the relative size of the CP-even and CP-odd couplings of a Higgs boson to tt can be determined at the LHC at a level that is very useful in discriminating between models, provided that a Higgs signal can be observed at a reasonable S/B level in the tth (with h→γγ or bb) channels. In particular, the CP-even nature of a SM-like Higgs bosonʹs coupling to tt can be confirmed with very substantial statistical significance using the tth (h→γγ) production/decay mode.