Leptoquark Flavor Patterns & B Decay Anomalies

TL;DR

This paper explores how flavor symmetries influence leptoquark couplings, leading to specific patterns that can explain B-decay anomalies and predict observable effects in various flavor-changing processes.

Contribution

It provides a framework linking flavor symmetries to leptoquark coupling patterns and their implications for B-decay anomalies and other flavor observables.

Findings

Maximal effects in R_D and R_D* around 10% and a few percent

Leptoquark effects in R_K(*) can reach a few times 10%

Predictions for charm, kaon decays, and mu-e conversion

Abstract

Flavor symmetries that explain masses and mixings of the standard model fermions dictate flavor patterns for the couplings of scalar and vector leptoquarks to the standard model fermions. A generic feature is that couplings to $SU(2)$-doublet leptons are suppressed at least by one spurion of the discrete non-abelian symmetry breaking, responsible for neutrino mixing, while couplings to charged lepton singlets can be order one. We obtain testable patterns including those that predominantly couple to a single lepton flavor, or two, or in a skewed way. They induce lepton non-universality, which we contrast to current anomalies in $B$-decays. We find maximal effects in $R_{D}$ and $R_{D^*}$ at the level of $\sim$10 percent and few percent, respectively, while leptoquark effects in $R_{K^{(*)}}$ can reach order few$\times 10$ percent. Predictions for charm and kaon decays and $\mu-e$ conversion are worked out.