$R_{K^{(*)}}$ and the origin of Yukawa couplings

TL;DR

This paper investigates the link between $R_{K^{(*)}}$ anomalies and the origin of Yukawa couplings, proposing a model combining vector-like families and gauged $U(1)'$ to explain flavor universality violation.

Contribution

It introduces a novel model merging vector-like families with gauged $U(1)'$ to connect $R_{K^{(*)}}$ anomalies with Yukawa coupling origins in the quark sector.

Findings

Connects $R_{K^{(*)}}$ anomalies to Yukawa couplings

Proposes a model with vector-like families and $U(1)'$ gauge symmetry

Requires tuning of Yukawa couplings for muon interactions

Abstract

We explore the possibility that the semi-leptonic $B$ decay ratios $R_{K^{(*)}}$ which violate $\mu - e$ universality are related to the origin of the fermion Yukawa couplings in the Standard Model. Some time ago, a vector-like fourth family (without a $Z'$) was used to generate fermion mass hierarchies and mixing patterns without introducing any family symmetry. Recently the idea of inducing flavourful $Z'$ couplings via mixing with a vector-like fourth family which carries gauged $U(1)'$ charges has been proposed as a simple way of producing controlled flavour universality violation while elegantly cancelling anomalies. We show that the fusion of these two ideas provides a nice connection between $R_{K^{(*)}}$ and the origin of Yukawa couplings in the quark sector. However the lepton sector requires some tuning of Yukawa couplings to obtain the desired coupling of $Z'$ to muons.