Probing the Higgs Yukawa coupling to the top-quark at the LHC via single top + Higgs production

Understand

The conjoined production at the LHC of single top and Higgs boson via $t$-channel weak boson exchange is ideal to probe the top-quark Yukawa coupling, due to a delicate cancellation between the amplitudes with the $htt$ and the $hWW$ couplings.

• We find that the top quark is produced with $100\%$ polarization in the leading order, and its quantum state is determined by the spin-vector direction in the $t$-quark rest frame.
• We relate the spin direction to the four-momenta of the top, Higgs and a jet in the helicity amplitude framework.
• We identify a polarization asymmetry that is sensitive to CP violation, even after partial integration over the forward jet momentum.