Abstract
We study consequences of CP violation in the \( ht\overline{t} \) Yukawa coupling through the process \( {e}^{+}{e}^{-}\to h(125)t\overline{t} \). The helicity amplitudes are calculated in the \( t\overline{t} \) 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 \( t\overline{t} \) plane about the Higgs momentum direction, but also in the correlated decay angular distributions of t and \( \overline{t} \). Complete description of the production and decay angular distributions are obtained analytically, including both leptonic and hadronic decays of t and \( \overline{t} \). We study the ultimate sensitivity to the CP-violating \( ht\overline{t} \) coupling at a few center-of-mass energies. Our analysis shows that the possibility of discovering CP-violating \( ht\overline{t} \) coupling improves significantly by studying \( t\overline{t} \) decay angular correlations, and more importantly, by increasing its energy upgrade target from \( \sqrt{s}=500 \) GeV to 550 GeV.
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References
ATLAS collaboration, Measurements of the Higgs boson production and decay rates and coupling strengths using pp collision data at \( \sqrt{s}=7 \) and 8 TeV in the ATLAS experiment, Eur. Phys. J. C 76 (2016) 6 [arXiv:1507.04548] [INSPIRE].
ATLAS and CMS collaborations, Measurements of the Higgs boson production and decay rates and constraints on its couplings from a combined ATLAS and CMS analysis of the LHC pp collision data at \( \sqrt{s}=7 \) and 8 TeV, JHEP 08 (2016) 045 [arXiv:1606.02266] [INSPIRE].
J.F. Gunion and X.-G. He, Determining the CP nature of a neutral Higgs boson at the LHC, Phys. Rev. Lett. 76 (1996) 4468 [hep-ph/9602226] [INSPIRE].
J. Ellis, D.S. Hwang, K. Sakurai and M. Takeuchi, Disentangling Higgs-top couplings in associated production, JHEP 04 (2014) 004 [arXiv:1312.5736] [INSPIRE].
F. Demartin, F. Maltoni, K. Mawatari, B. Page and M. Zaro, Higgs characterisation at NLO in QCD: CP properties of the top-quark Yukawa interaction, Eur. Phys. J. C 74 (2014) 3065 [arXiv:1407.5089] [INSPIRE].
S. Khatibi and M. Mohammadi Najafabadi, Exploring the anomalous Higgs-top couplings, Phys. Rev. D 90 (2014) 074014 [arXiv:1409.6553].
X.-G. He, G.-N. Li and Y.-J. Zheng, Probing Higgs boson CP properties with \( t\overline{t}H \) at the LHC and the 100 TeV pp collider, Int. J. Mod. Phys. A 30 (2015) 1550156 [arXiv:1501.00012] [INSPIRE].
M.R. Buckley and D. Goncalves, Boosting the direct CP measurement of the Higgs-top coupling, Phys. Rev. Lett. 116 (2016) 091801 [arXiv:1507.07926] [INSPIRE].
S. Biswas, E. Gabrielli and B. Mele, Single top and Higgs associated production as a probe of the Htt coupling sign at the LHC, JHEP 01 (2013) 088 [arXiv:1211.0499] [INSPIRE].
C. Englert and E. Re, Bounding the top Yukawa coupling with Higgs-associated single-top production, Phys. Rev. D 89 (2014) 073020 [arXiv:1402.0445] [INSPIRE].
F. Demartin, F. Maltoni, K. Mawatari and M. Zaro, Higgs production in association with a single top quark at the LHC, Eur. Phys. J. C 75 (2015) 267 [arXiv:1504.00611] [INSPIRE].
G. Bhattacharyya, D. Das and P.B. Pal, Modified Higgs couplings and unitarity violation, Phys. Rev. D 87 (2013) 011702 [arXiv:1212.4651] [INSPIRE].
D. Choudhury, R. Islam and A. Kundu, Anomalous Higgs couplings as a window to new physics, Phys. Rev. D 88 (2013) 013014 [arXiv:1212.4652] [INSPIRE].
S. Bar-Shalom, D. Atwood, G. Eilam, R.R. Mendel and A. Soni, Large tree level CP-violation in \( {e}^{+}{e}^{-}\to t\overline{t}{H}^0 \) in the two Higgs doublet model, Phys. Rev. D 53 (1996) 1162 [hep-ph/9508314] [INSPIRE].
P.S. Bhupal Dev et al., Determining the CP properties of the Higgs boson, Phys. Rev. Lett. 100 (2008) 051801 [arXiv:0707.2878] [INSPIRE].
K. Hagiwara, K. Ma and H. Yokoya, Probing CP-violation in e + e − production of the Higgs boson and toponia, JHEP 06 (2016) 048 [arXiv:1602.00684] [INSPIRE].
L. Wolfenstein, Violation of CP invariance and the possibility of very weak interactions, Phys. Rev. Lett. 13 (1964) 562 [INSPIRE].
J. Alwall et al., The automated computation of tree-level and next-to-leading order differential cross sections and their matching to parton shower simulations, JHEP 07 (2014) 079 [arXiv:1405.0301] [INSPIRE].
C. Farrell and A.H. Hoang, The large Higgs energy region in Higgs associated top pair production at the linear collider, Phys. Rev. D 72 (2005) 014007 [hep-ph/0504220] [INSPIRE].
C. Farrell and A.H. Hoang, Next-to-leading-logarithmic QCD corrections to the cross-section \( \sigma \left({e}^{+}{e}^{-}\to t\overline{t}H\right) \) at 500 GeV, Phys. Rev. D 74 (2006) 014008 [hep-ph/0604166] [INSPIRE].
R. Yonamine et al., Measuring the top Yukawa coupling at the ILC at \( \sqrt{s}=500 \) GeV, Phys. Rev. D 84 (2011) 014033 [arXiv:1104.5132] [INSPIRE].
Y. Sumino and H. Yokoya, Bound-state effects on kinematical distributions of top quarks at hadron colliders, JHEP 09 (2010) 034 [Erratum ibid. 1606 (2016) 037] [arXiv:1007.0075] [INSPIRE].
S.-F. Ge, K. Hagiwara, N. Okamura and Y. Takaesu, Determination of mass hierarchy with medium baseline reactor neutrino experiments, JHEP 05 (2013) 131 [arXiv:1210.8141] [INSPIRE].
K. Hagiwara and D. Zeppenfeld, Helicity amplitudes for heavy lepton production in e + e − annihilation, Nucl. Phys. B 274 (1986) 1 [INSPIRE].
K. Hagiwara, H. Murayama and I. Watanabe, Search for the Yukawa interaction in the process \( {e}^{+}{e}^{-}\to t\overline{t}Z \) at TeV linear colliders, Nucl. Phys. B 367 (1991) 257 [INSPIRE].
H. Murayama, I. Watanabe and K. Hagiwara, HELAS: HELicity amplitude subroutines for Feynman diagram evaluations, KEK-91-11 (1991).
T. Stelzer and W.F. Long, Automatic generation of tree level helicity amplitudes, Comput. Phys. Commun. 81 (1994) 357 [hep-ph/9401258] [INSPIRE].
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Hagiwara, K., Yokoya, H. & Zheng, YJ. Probing the CP properties of top Yukawa coupling at an e+e− collider. J. High Energ. Phys. 2018, 180 (2018). https://doi.org/10.1007/JHEP02(2018)180
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DOI: https://doi.org/10.1007/JHEP02(2018)180