Neutrino masses in a 5D SU(3)W TeV unification model

We study the generation of neutrino masses in the SU(3)(W) electroweak unified theory in M-4 x S-1/(Z(2) x Z(2)') spacetime. By appropriate orbifolding, the bulk symmetry SU(3)(W) is broken into SU(2)(L) x U(1)(Y) at one of the fixed points, where the quarks reside. The leptons form SU(3)(W) triplets, localized at the other symmetric fixed point. The fermion masses arise from the bulk Higgs sector containing a triplet and an anti-sextet. We construct neutrino Majorana masses via 1-loop quantum corrections by adding a parity odd bulk triplet scalar. No right-handed neutrino is needed. The neutrino mass matrix is of the inverted hierarchy type. We show that the model can easily accommodate the bi-large mixing angle solution favored by the recent neutrino experiments without much fine tuning of parameters. The constraints from mu --> 3e transition and neutrinoless double beta decays are discussed. Crown copyright (C) 2003 Published by Elsevier Science B.V. All rights reserved.