  This study utilises the Higgs Characterization model to investigate the $CP$
properties of the Higgs coupling to the top quark using the $tH$ and
$t\bar{t}H$ generation processes. This is done via simulations of proton-proton
collisions with ATLAS detector conditions, which are calculated for seven
different $CP$ eigenstates using MadGraph5_aMC@NLO. Three orthogonal categories
of cuts are subsequently implemented to find the cut efficiencies, which are
used in conjunction with the cross-section to find the signal strength.
Comparing the signal strength with experimental results shows that one cannot
yet conclusively rule out any Higgs $CP$ eigenstates. Analysing histograms
showed that the most $CP$ sensitive variables were the transverse momenta of
the Higgs, leptons and photons, which showed a hardening as the Higgs coupling
became $CP$ odd.
