Tri-bimaximal neutrino mixing from discrete symmetry in extra dimensions Original Research Article

We discuss a particularly symmetric model of neutrino mixings where, with good accuracy, the atmospheric mixing angle image is maximal, image and the solar angle satisfies image (Harrison–Perkins–Scott (HPS) matrix). The discrete symmetry image is a suitable symmetry group for the realization of this type of model. We construct a model where the HPS matrix is exactly obtained in a first approximation without imposing ad hoc relations among parameters. The crucial issue of the required VEV alignment in the scalar sector is discussed and we present a natural solution of this problem based on a formulation with extra dimensions. We study the corrections from higher dimensionality operators allowed by the symmetries of the model and discuss the conditions on the cut-off scales and the VEVs in order for these corrections to be completely under control. Finally, the observed hierarchy of charged lepton masses is obtained by assuming a larger flavour symmetry. We also show that, under general conditions, a maximal image can never arise from an exact flavour symmetry.