Neutrino masses in supersymmetric SU(3)CxSU(2)LxU(1)YxU(1)′ models -: art. no. 015012

We consider various possibilities for generating neutrino masses in supersymmetric models with an additional U(1)(') gauge symmetry. One class of models involves two extra U(1)'xU(1)" gauge symmetries, with U(1)" breaking at an intermediate scale and yielding small Dirac masses through high-dimensional operators. The right-handed neutrinos N-i(c) can naturally decouple from the low energy U(1)', avoiding cosmological constraints. A variant version can generate large Majorana masses for N-i(c) and an ordinary seesaw. We secondly consider models with a pair of heavy triplets which couple to left-handed neutrinos. After integrating out the heavy triplets, a small neutrino Majorana mass matrix can be generated by the induced nonrenormalizable terms. We also study models involving the double-seesaw mechanism, in which heavy Majorana masses for N-i(c) are associated with the TeV-scale of U(1)' breaking. We give the conditions to avoid runaway directions in such models and discuss simple patterns for neutrino masses.