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Better Higgs- CP tests through information geometry

Physical Review D (2018) 97(9)
DOI: 10.1103/PhysRevD.97.095017
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Abstract

Measuring the CP symmetry in the Higgs sector is one of the key tasks of the LHC and a crucial ingredient for precision studies, for example in the language of effective Lagrangians. We systematically analyze which LHC signatures offer dedicated CP measurements in the Higgs-gauge sector and discuss the nature of the information they provide. Based on the Fisher information measure, we compare the maximal reach for CP-violating effects in weak boson fusion, associated ZH production, and Higgs decays into four leptons. We find a subtle balance between more theory-independent approaches and more powerful analysis channels, indicating that rigorous evidence for CP violation in the Higgs-gauge sector will likely require a multistep process.

Figures

  • FIG. 1. Feynman diagrams describing the three processes considered in this paper: WBF Higgs production, associated ZH production, and H → 4l decays.
  • TABLE I. Predictions for CP-odd observables O based on the theory’s symmetries and the observable’s transformation properties under T̂. In all cases we assume that the initial state or its probability distribution is symmetric under both CP and T̂.
  • FIG. 2. Distribution of the signed angle Δϕjj in WBF Higgs production after the cuts in Eqs. (27) and (29) for the Standard Model (black) as well as the for the EFTwith the indicated Wilson coefficients. In the left panel we show the SM signal (black) as well as the interference of different dimension-six amplitudes with the SM signal (colored). The right panel shows the full distributions including the backgrounds (grey).
  • FIG. 3. Optimal 1σ contours for WBF Higgs production with H → ττ (solid black). Also shown are the results based on different subsets of the Δϕjj distribution, including its absolute value (purple), its asymmetry (orange), its full distribution (red), its combination with the leading jet pT distribution (blue); as well as the observableO as defined in Eq. (23) (green). In grey we show bounds based on a simple rate measurement. In each panel, the parameters not shown are set to zero.
  • FIG. 4. Distributions of Δϕll (left) and ΔEll (right) in ZH production after the cuts in Eqs. (38) and (40) for the Standard Model signal (solid black), and for the interference between different dimension-six amplitudes with the SM signal (colored).
  • FIG. 5. Optimal 1σ contours for ZH production (solid black). The colored lines show the reach contained in the Δϕll distribution, including its absolute value (orange), asymmetry (green), full distribution (red), combination with the mZH distribution (blue); based on the distribution of ΔEll (purple); for the distribution of ΔpT;ll (turquoise); and based on a simple rate measurement (grey). In each panel, the parameters not shown are set to zero.
  • FIG. 6. Optimal 1σ contours for gg → h → 4l (solid black). In grey we show bounds based on a rate measurement. The red line shows the contours based on an analysis of the lower of the two lepton pair masses mZ2 and Φ, other kinematic variables lead to bounds between the red and grey lines. In each panel, the parameters not shown are set to zero.
  • FIG. 7. Comparison of the sensitivity of different channels and observables at the LHC with 100 fb−1. In the top panel we show the eigenvalues of the various Fisher information matrices. The colors denote the decomposition of the corresponding eigenvectors: the length of each segment is proportional to the magnitude of the eigenvector component. In the bottom panel we show the Fisher information on the CP-violating Wilson coefficient fWW̃ . The grey bars show the sensitivity assuming that all other considered operators are zero, while the red bars profile over arbitrary values of all of the CP-even parameters (including absorptive parts). In both panels, the right axes translate the Fisher information into the corresponding new physics reach.

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CITATION STYLE

APA

Brehmer, J., Kling, F., Plehn, T., & Tait, T. M. P. (2018). Better Higgs- CP tests through information geometry. Physical Review D, 97(9). https://doi.org/10.1103/PhysRevD.97.095017

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