Non-abelian gauge extensions for B-decay anomalies

TL;DR

This paper explores minimal non-abelian gauge extensions of the Standard Model to explain recent B-decay anomalies, classifying models by symmetry-breaking patterns and proposing a specific model consistent with experimental constraints.

Contribution

It classifies gauge extension models based on symmetry-breaking and flavor non-universality sources, and presents a concrete model explaining B-decay anomalies.

Findings

Viable models embed SU(2)_L non-trivially in the extended gauge group.

Gauge couplings should be universal in these models.

An explicit model successfully explains B-decay anomalies.

Abstract

We study the generic features of minimal gauge extensions of the Standard Model in view of recent hints of lepton-flavor non-universality in semi-leptonic $b \to s \ell^+ \ell^-$ and $b \to c \ell \nu$ decays. We classify the possible models according to the symmetry-breaking pattern and the source of flavor non-universality. We find that in viable models the $\mathrm{SU(2)}_L$ factor is embedded non-trivially in the extended gauge group, and that gauge couplings should be universal, hinting to the presence of new degrees of freedom sourcing non-universality. Finally, we provide an explicit model that can explain the $B$-decay anomalies in a coherent way and confront it with the relevant phenomenological constraints.