Tri-bimaximal lepton mixing from symmetry only
Abstract
We construct a model for tri-bimaximal lepton mixing which employs only family symmetries and their soft breaking; neither vacuum alignment nor supersymmetry, extra dimensions, or non-renormalizable terms are used in our model. It is an extension of the Standard Model making use of the seesaw mechanism with five right-handed neutrino singlets. The scalar sector comprises four Higgs doublets and one complex gauge singlet. The horizontal symmetry of our model is based on the permutation group S3 of the lepton families together with the three family lepton numbers--united this constitutes a symmetry group Delta(6∞2). The model makes no predictions for the neutrino masses.
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