Neutrino mixings from a U(2) flavour symmetry

TL;DR

This paper extends a U(2) flavour symmetry model to explain neutrino mixing angles and mass hierarchies, providing unified descriptions and specific predictions for lepton and quark mixing matrix elements based on mass ratios.

Contribution

It introduces a unified U(2) flavour symmetry framework that accounts for large neutrino mixing angles and mass hierarchies, linking them to quark sector relations.

Findings

Predicts |V_{μ1}| = |V_{e3}/V_{μ3}| = |V_{e2}/V_{τ3}| = √(me/mμ)

Establishes analogous relations in the quark sector: |V_{ub}/V_{cb}| = √(mu/mc)

Provides quantitative predictions for lepton mixing matrix elements.

Abstract

We extend a previously developed description of the flavour parameters in the charged fermion sector, based on a U(2) flavour symmetry, to include two main features of the neutrino sector seemingly implied by recent data: a large mixing angle $\theta_{\mu \tau}$ and a large hierarchy in the neutrino squared mass differences. A unified description of quark and lepton masses and mixings emerges. The neatest quantitative predictions are for elements of the unitary mixing matrix in the lepton sector: |V_{\mu 1}| = |V_{e 3} / V_{\mu 3}| = |V_{e 2} / V_{\tau 3}| = \sqrt{m_e / m_\mu}, which go together with the analogous relations in the quark sector: |V_{ub} / V_{cb}| = \sqrt{m_u / m_c}, |V_{td} / V_{ts}| = \sqrt{m_d / m_s}