Journal of High Energy Physics

, 2018:69 | Cite as

\( {R}_{K^{\left(*\right)}} \) and the origin of Yukawa couplings

  • Stephen F. KingEmail author
Open Access
Regular Article - Theoretical Physics


We explore the possibility that the semi-leptonic B decay ratios \( {R}_{K^{\left(*\right)}} \) which violate μe 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 \( {R}_{K^{\left(*\right)}} \) 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.


Beyond Standard Model Heavy Quark Physics Neutrino Physics Quark Masses and SM Parameters 


Open Access

This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.


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© The Author(s) 2018

Authors and Affiliations

  1. 1.Department of Physics and AstronomyUniversity of SouthamptonSouthamptonU.K.

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