Top Yukawa coupling measurement with indefinite CP Higgs in $e^{+}{e}^{-}\to t\bar{t}\Phi$

Abstract

We consider the issue of the top quark Yukawa coupling measurement in a model in dependent and general case with the inclusion of CP-violation in the coupling. Arguably the best process to study this coupling is the associa ted production of Higgs boson along with a $t\bar{t}$ pair in a machine like the International Linear Collider (ILC). While detailed analyses of the sensitivity of the measurement assuming a Standard Model (SM) - like coupling are available in the context of ILC, conclude that th e coupling could be pinned down at about 10\% level with modest luminosity, our investigations show that the scenario could be different in case of a more general coupling. The modified Lorentz structure resulting in a changed functional dependence of the cross section on the couplin g, along with the difference in the cross section itself leads to considerable deviation in the sensitivity. Our studies with an ILC of center of mass energies of 500 GeV, 800 GeV and 1000 GeV show that moderate CP-mixing in the Higgs sector could change the sensitivity to about 20\ %, while it could be worsened to 75\% in cases which could accommodate more dramatic changes in the coupling. While detailed considerations of the decay distributions point to a need for a relook at the analysis strategy followed for the case of SM such as for a model independent analysis of the top quark Yukawa coupling measurement. This study strongly suggests that, a joint analysis of the CP properties and the Yukawa coupling measurement would be the way forward at the ILC and that caution must be excercised in the measurem ent of the Yukawa couplings and the conclusions drawn from it.

18 pages, 7 figures, uses revtex

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• Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
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• Determining the CP properties of the Higgs boson
• Probing the Top-Yukawa Coupling in Associated Higgs production with a Single Top Quark
• Measuring the top Yukawa coupling at the ILC at sqrt(s) = 500 GeV
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Cited by in corpus (4)

• Exploring the Anomalous Higgs-top Couplings
• Study of Higgs-gauge boson anomalous couplings through $e^{-}{e}^{+}\to W^{-}{W}^{+}H$ at ILC
• Measuring Higgs self couplings in the presence of VVH and VVHH at the ILC
• Influence of anomalous VVH and VVHH on determination of Higgs self couplings at ILC