Seesaw Neutrino Mass and New U(1) Gauge Symmetry

Abstract

The three electroweak doublet neutrinos ${\nu }_{e,\mu ,\tau }$ of the Standard Model may acquire small seesaw masses, using either three Majorana fermion singlets $N$ or three Majorana fermion triplets $({\Sigma }^{+},{\Sigma }^0,{\Sigma }^{-})$. It is well-known that the former accommodates the U(1) gauge symmetry $B-L$. It has also been shown some years ago that the latter supports a new $U(1{)}_X$ gauge symmetry. Here we study two variations of this $U(1{)}_X$, one for two $N$ and one $\Sigma$, the other for one $N$ and two $\Sigma$. Phenomenological consequences are discussed.

Comments: 16 pages, 3 figures, LaTex, 2 eps files,text added