Neutrino mixings from a U(2) flavour symmetry

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 $θ_{μτ}$ 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_{μ1}| = |V_{e 3} / V_{μ3}| = |V_{e 2} / V_{τ3}| = \sqrt{m_e / m_μ}, 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}