Probing the CP nature of the Higgs coupling in $t{\bar t}h$ events at the LHC

Understand

The determination of the CP nature of the Higgs coupling to top quarks is addressed in this paper, using $t{\bar t} h$ events produced in $\sqrt{s} = 13$ TeV proton-proton collisions at the LHC.

• Dileptonic final states are employed, with two oppositely charged leptons and four jets, corresponding to the decays $t\rightarrow bW^+ \rightarrow b \ell^+\nu_\ell$, $\bar{t}\rightarrow \bar{b}W^- \rightarrow \bar{b} \ell^-\bar{\nu}_\ell$ and $h\rightarrow b\bar{b}$.
• Pure scalar ($h=H$), pure pseudo-scalar ($h=A$) and CP-violating Higgs boson signal events, generated with MadGraph5_aMC@NLO, are fully reconstructed through a kinematic fit.
• We furthermore generate samples that have both a CP-even and a CP-odd component in the $t \bar t h$ coupling in order to probe the ratio of the two components.