Flavour from the Planck scale to the electroweak scale

Abstract

We discuss a theory of flavour in which Higgs Yukawa couplings are related to those of the new scalar triplet leptoquark and/or $Z^{\prime }$ responsible for $R_{K^{(\ast )}}$, with all couplings arising effectively from mixing with a vector-like fourth family, whose mass may be anywhere from the Planck scale to the electroweak scale for the leptoquarks explanation, but is pinned down to the TeV scale if the $Z^{\prime }$ exchange plays a role. However, in this particular model, only leptoquark exchange can contribute significantly to $R_{K^{(\ast )}}$, since $Z^{\prime }$ exchange is too constrained from $B_s$ mixing and $\tau \to 3\mu$, although other Higgs Yukawa matrix structures may allow it.

Comments: 6 pages, 11 figures. Contribution to the 2019 EW session of the 54th Rencontres de Moriond