Lepton Flavor and Non-Universality from Minimal Composite Higgs Setups

TL;DR

This paper introduces a minimal composite Higgs model that explains lepton flavor phenomena, including the LHCb $R_K$ anomaly, while maintaining flavor protection and reducing the need for ultra-light top partners.

Contribution

It proposes a predictive minimal composite Higgs framework unifying right-handed leptons, addressing lepton flavor non-universality and flavor anomalies with enhanced Higgs mass corrections.

Findings

Addresses the $R_K$ anomaly in B decays.

Provides flavor protection reducing FCNCs.

Links top partner masses with neutrino masses.

Abstract

We present a new class of models of lepton flavor in the composite Higgs framework. Following the concept of minimality, they lead to a rich phenomenology in good agreement with the current experimental picture. Because of a unification of the right-handed leptons, our scenario is very predictive and can naturally lead to a violation of lepton-flavor universality in neutral current interactions. We will show that, in particular, the anomaly in $R_K= {\cal B}(B \to K \mu^+ \mu^-)/{\cal B}(B \to K e^+ e^-)$, found by LHCb, can be addressed, while other constraints from quark- and lepton-flavor physics are met. In fact, the minimal structure of the setup allows for the implementation of a very powerful flavor protection, which avoids the appearance of new sources of flavor-changing neutral currents to very good approximation. Finally, the new lepton sector provides a parametrically enhanced correction to the Higgs mass, such that the need for ultra-light top partners is weakened considerably, linking the mass of the latter with the size of the neutrino masses.