Probing the top Yukawa coupling at the LHC via associated production of single top and Higgs

Abstract

We study Higgs boson production associated with single top or anti-top via $t$-channel weak boson exchange at the LHC. The process is an ideal probe of the top quark Yukawa coupling, because we can measure the relative phase of $htt$ and $hWW$ couplings, thanks to the significant interference between the two amplitudes. By choosing the emitted $W$ momentum along the polar axis in the $th(\bar{t}h)$ rest frame, we obtain the helicity amplitudes for all the contributing subprocesses analytically, with possible CP phase of the Yukawa coupling. We study the azimuthal asymmetry between the $W$ emission and the $Wb(\bar{b})\to t(\bar{t})h$ scattering planes, as well as several $t$ and $\bar{t}$ polarization asymmetries as a signal of CP violating phase in the $htt$ coupling. Both the azimuthal asymmetry and the polarization perpendicular to the scattering plane are found to have the opposite sign between the top and anti-top events. We identify the origin of the sign of asymmetries, and propose the possibility of direct CP violation test in $pp$ collisions by comparing the top and anti-top polarization at the LHC.

arXiv comment31 pages, 19 figures and 2 tables; references added

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Cited by in corpus (4)

• Collider Physics at the Precision Frontier
• Probing the CP Structure of the Top Quark Yukawa at the Future Muon Collider
• Analytical Insights on Hadronic Top Quark Polarimetry
• Sensitivity to $\mathcal{C}\mathcal{P}$-violating effective couplings in the top-Higgs sector