A Bottom-Up Approach: The Data Driven Flavour Model

TL;DR

This paper proposes a bottom-up, data-driven flavour model that explains fermion mass hierarchies and mixings using a specific flavour symmetry and spurion fields, aligning with experimental observations.

Contribution

It introduces a novel bottom-up approach combining $U(2)$ and $U(3)$ symmetries, incorporating dynamical spurions to reproduce fermion masses and mixings.

Findings

Model aligns with experimental fermion mass hierarchies

Flavour protection similar to Minimal Flavour Violation

Scalar potential with a stable minimum reproduces observed mixings

Abstract

A bottom-up approach has been adopted to identify a flavour model that agrees with present experimental measurements. The charged fermion mass hierarchies suggest that only the top Yukawa term should be present at the renormalisable level. The flavour symmetry of the Lagrangian including the fermionic kinetic terms and only the top Yukawa is then a combination of $U(2)$ and $U(3)$ factors. Lighter charged fermion and active neutrino masses and quark and lepton mixings arise considering specific spurion fields. The associated phenomenology is investigated and the model turns out to have almost the same flavour protection of the Minimal Flavour Violation, in both quark and lepton sectors. Promoting the spurions to be dynamical fields, the associated scalar potential is also studied and a minimum is identified such that fermion masses and mixings are correctly reproduced.