Little Higgs and Custodial SU(2)

209 citations (202 excluding self-citations). Extended the Minimal Moose by incorporating custodial symmetry, the key ingredient for compatibility with precision electroweak data.

The Problem

The original Little Higgs models generated contributions to the T parameter (the oblique correction measuring custodial SU(2) violation) that were in tension with precision electroweak measurements unless the symmetry-breaking scale f was pushed above 2-3 TeV. At those scales, the fine-tuning the models were designed to eliminate begins to reappear. The question was whether a Little Higgs model could be built with custodial SU(2) as an approximate symmetry, suppressing the T parameter and allowing a lower breaking scale with accessible new particles.

The Key Idea

The paper modifies the Minimal Moose construction by replacing the SU(3) gauge symmetries with SO(5), which contains custodial SU(2) as a subgroup. In a simple limit, the heavy W’ and B’ make small contributions to precision observables. The result: the breaking scale can be as low as 700 GeV, with a top partner at 2 TeV, W’ and B’ at 2.5 TeV, and heavy Higgs partners at 2 TeV — all accessible at the LHC. The model predicts two Higgs doublets at low energies and favors a light Higgs from precision constraints, though for different structural reasons than in the Standard Model.

Recollections

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• DOI
• arXiv:hep-ph/0303001
• INSPIRE