Custodial Isospin Violation in the Lee-Wick Standard Model

Abstract

We analyze the tension between naturalness and isospin violation in the Lee-Wick Standard Model (LW SM), by computing tree-level and fermionic one-loop contributions to the post-LEP electroweak parameters and the Zbb coupling. The model is most natural when the LW partners of the gauge bosons and fermions are light, but small partner masses can lead to large isospin violation. The post-LEP parameters yield a simple picture in the LW SM: the gauge sector contributes to Y and W only, with leading contributions arising at tree-level, while the fermion sector contributes to S-hat and T-hat only, with leading corrections arising at one loop. Hence, W and Y constrain the masses of the LW gauge bosons to satisfy M1, M2 > 2.4 TeV at 95% CL. Likewise, experimental limits on T-hat reveal that the masses of the LW fermions must satisfy Mq, Mt > 1.6 TeV at 95% CL if the Higgs mass is light and tend to exclude the LW SM for any LW fermion masses if the Higgs mass is heavy. Contributions from the top-quark sector to the Zbb coupling can be even more stringent, placing a lower bound of 4 TeV on the LW fermion masses at 95% CL.

16 pages, 8 embedded eps figures

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• The Limits of Custodial Symmetry

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• A Radiation Bounce from the Lee-Wick Construction?
• Global Symmetries and Renormalizability of Lee-Wick Theories
• Ultraviolet Properties of the Higgs Sector in the Lee-Wick Standard Model
• A Conducting surface in Lee-Wick electrodynamics
• LHC Constraints on the Lee-Wick Higgs Sector
• Probing features of the Lee-Wick quantum electrodynamics
• Collider Bounds on Lee-Wick Higgs Bosons
• Collider Signatures of the N=3 Lee-Wick Standard Model
• The Lee-Wick Standard Model at Finite Temperature
• Precision Electroweak Constraints on the N=3 Lee-Wick Standard Model
• Acausality from a Dark Sector
• About the triviality of the higher derivative sector in the abelian Lee-Wick model
• The Lee-Wick Extension of the Two-Higgs Doublet Model