Exploring the Anomalous Higgs-top Couplings

Top quark with its large Yukawa coupling is crucially important to explore TeV scale physics. Therefore, the study of Higgs-top sector is highly motivated to look for any deviations from the standard model predictions. The most general lowest order Lagrangian for the Higgs-top Yukawa coupling has scalar ($κ$) and pseudoscalar ($\tildeκ$) components. Currently, these couplings are constrained indirectly using the present experimental limits on the Higgs-$γ$-$γ$ and Higgs-gluon-gluon couplings. Furthermore, stronger bounds on $κ$ and $\tildeκ$ are obtained using the limits on the electric dipole moments (EDM). In this work, we propose an asymmetry-like observable $O_ϕ$ in $t\bar{t}H$ production at the LHC to probe the Higgs-top coupling and to distinguish between the scalar and pseudoscalar components. We also show that the presence of the pseudoscalar component in the Higgs-top Yukawa coupling leads to a sizeable value for the top quark EDM. It is shown that a limit of $10^{-19}$ e.cm, which is achievable by the future $e^{-}e^{+}$ collider, allows us to exclude a significant region in the $(κ,\tildeκ)$ plane.

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