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arXiv · 1712.09953

Probing the CP properties of top Yukawa coupling at an $e^+e^-$ collider

Kaoru Hagiwara·Hiroshi Yokoya·Ya-Juan Zheng
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Abstract

We study consequences of CP violation in the $ht\bar{t}$ Yukawa coupling through the process $e^+e^- \to$ $h(125)t\bar{t}$. The helicity amplitudes are calculated in the $t\bar{t}$ rest frame, where the initial $e^+e^-$ current and the final Higgs boson have the same three-momentum. CP-violating asymmetries appear not only in the azimuthal angle between the $e^+e^-$ plane and the $t\bar{t}$ plane about the Higgs momentum direction, but also in the correlated decay angular distributions of $t$ and $\bar{t}$. Complete description of the production and decay angular distributions are obtained analytically, including both leptonic and hadronic decays of $t$ and $\bar{t}$. We study the ultimate sensitivity to the CP-violating $ht\bar{t}$ coupling at a few center-of-mass energies. Our analysis shows that the possibility of discovering CP violating $ht\bar{t}$ coupling improves significantly by studying $t\bar{t}$ decay angular correlations, and more importantly, by increasing its energy upgrade target from $\sqrt{s} = 500$ GeV to 550 GeV.

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Kaoru Hagiwara, Hiroshi Yokoya, Ya-Juan Zheng. 2018-02-19. Probing the CP properties of top Yukawa coupling at an $e^+e^-$ collider. https://doi.org/10.1007/jhep02(2018)180

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