SU(3) family symmetry and neutrino bi-tri-maximal mixing

The observed large mixing angles in the lepton sector may be the first signal for the presence of a nonAbelian family symmetry. However, to obtain the significant differences between the mixing of the neutrino and charged fermion sectors, the vacuum expectation values involved in the breaking Of Such a symmetry in the two sectors must be misaligned. We investigate how this can be achieved in models with an SU(3)/family symmetry consistent with an underlying GUT. We show that such misalignment can be achieved naturally via the see-saw mechanism. We construct a specific example in which the vacuum (mis)alignment is guaranteed by additional symmetries. This model generates a fermion mass structure consistent with all quark and lepton masses and mixing angles. Neutrino mixing is close to bi-tri-maximal mixing. (c) 2005 Elsevier B.V. All rights reserved.