Lepton flavour universality violation from composite muons

TL;DR

This paper proposes a minimal composite Higgs model where partially composite muons explain the LHCb observed deviation in lepton flavor universality, also predicting effects on B_s mixing and Z width.

Contribution

It introduces a novel minimal composite Higgs framework with muon compositeness to explain flavor anomalies and predicts related new physics effects.

Findings

Good fit to LHCb anomaly with muon compositeness

Predicts new contributions to B_s mixing

Accounts for LEP Z width deficit

Abstract

We describe a possibility to explain the $2.6\sigma$ deviation from lepton flavour universality observed by the LHCb collaboration in $B^+\to K^+\ell^+\ell^-$ decays in the context of minimal composite Higgs models. We find that a sizable degree of compositeness of partially composite muons can lead to a good agreement with the experimental data. Our construction predicts a new physics contribution to $B_s$-$\bar{B}_s$ mixing. Additionally, it accounts for the deficit in the invisible $Z$ width measured at LEP.