Dirac neutrinos from flavor symmetry

Abstract

We present a model where Majorana neutrino mass terms are forbidden by the flavor symmetry group $\mathrm{\ensuremath{\Delta}}(27)$. Neutrinos are Dirac fermions and their masses arise in the same way as those of the charged fermions, due to very small Yukawa couplings. The model fits current neutrino oscillation data and correlates the octant of the atmospheric angle ${\ensuremath{\theta}}_{23}$ with the magnitude of the lightest neutrino mass, with maximal mixing excluded for any neutrino mass hierarchy.