Abstract
We propose a theory for fermion masses and mixings in which an A4 family symmetry arises naturally from a six-dimensional spacetime after orbifold compactification. The flavour symmetry leads to the successful “golden” quark-lepton unification formula. The model reproduces oscillation parameters with good precision, giving sharp predictions for the CP violating phases of quarks and leptons, in particular δℓ≃+268∘. The effective neutrinoless double-beta decay mass parameter is also sharply predicted as 〈mββ〉≃2.65meV.
Highlights
The historical discovery of neutrino oscillations [1,2] implies the need for neutrino masses on the one hand, and a way to understand the special pattern of lepton mixing angles on the other [3]
In this work we have proposed an A4 theory for fermion masses and mixings in which the family symmetry emerges naturally from a six-dimensional spacetime after orbifold compactification
The A4 remnant flavour symmetry leads to the successful “golden” quark-lepton unification formula in Eq (15) and Fig. 1
Summary
The historical discovery of neutrino oscillations [1,2] implies the need for neutrino masses on the one hand, and a way to understand the special pattern of lepton mixing angles on the other [3] This has spurred interest in understanding the theoretical origin of neutrino mass and the understanding of flavour parameters. We use the framework of 6-dimensional theories compactified on a torus [8,9] This way we obtain a predictive model for fermion masses and mixings in which the family symmetry A4 emerges naturally as a remnant symmetry after orbifold compactification. In contrast to the original A4 proposal in [10], the present realization makes predictions for fermion mass hierarchies, not just angles and phases It predicts the “golden” quark-lepton unification formula, which emerges in other schemes [11,12,13,14].
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