The structure of electroweak corrections due to extended gauge symmetries

TL;DR

This work presents the Generalized BESS (GBESS) framework for extended electroweak gauge sectors, unifying a variety of models with replicated gauge groups under a moose-based description. It shows that the pattern and size of corrections to precision electroweak observables depend critically on how Standard Model fermions transform under the extended gauge structure, with Case I yielding fourth-power suppression in the new-physics scales and Cases II–IV exhibiting only second-power suppression. Through both low-energy (four-fermion operators) and Z-pole analyses, the authors derive how masses and couplings of the W and Z are modified, including explicit expressions for light-boson couplings and heavy-boson spectra. A global fit to precision data for flavor-universal GBESS (Case I) finds no improvement over the Standard Model and yields constraints that typically push the new-physics scale $f$ to a few TeV, with stronger bounds arising from the $\sin\phi$-dependent sector. The results clarify how various published models fit within GBESS and explain why certain constructions naturally evade stringent constraints, while providing a practical roadmap for evaluating extended electroweak theories against data.

Abstract

This paper studies models with extended electroweak gauge sectors of the form SU(2) x SU(2) x U(1) x [SU(2) or U(1)]. We establish the general behavior of corrections to precision electroweak observables in this class of theories and connect our results to previous work on specific models whose electroweak sectors are special cases of our extended group.

Figures (2)

• Figure 1: Constraints on $c_1$ and $c_2$ at the 68%, 95%, and 99% confidence level based on fits to precision electroweak data.Group:2002mc
• Figure 2: The lower-bound on $f$ at 95% confidence level for $\alpha=\pi/4$, as a function of $\sin\omega$ and $\sin\phi$, based on fits to precision electroweak data.Group:2002mc