Neutrinos, their partners, and unification

Abstract.

Efforts to unify group-theoretically the standard-model gauge interactions with the generation structure of fermions and their mirror partners should be accompanied by the unification of the corresponding gauge couplings. In this paper, the possibility of such a unification is studied, and conclusions on possible symmetry-breaking channels and scales as well as on the fermion content of the theory are drawn. The breaking of some of the symmetries allows various Majorana masses for neutrinos and their mirror partners, so these are studied next. Implications for neutrino mixings and mass hierarchies in connection with recent experimental results, as well as for electroweak precision tests, are then discussed.