Radiatively Induced Neutrino Masses and Oscillations in an SU(3)_LxU(1)_N Gauge Model

Abstract

We have constructed an $SU(3{)}_L\times U(1{)}_N$ gauge model utilizing an $U(1{)}_{L^{\prime }}$ symmetry, where $L^{\prime }$ = $L_e-L_{\mu }-L_{\tau }$, which accommodates tiny neutrino masses generated by $L^{\prime }$-conserving one-loop and $L^{\prime }$-breaking two-loop radiative mechanisms. The generic smallness of two-loop radiative effects compared with one-loop radiative effects describes the observed hierarchy of $\Delta m_{atm}^2$ $\gg$ $\Delta m_{\odot }^2$. A key ingredient for radiative mechanisms is a charged scalar ($h^{+}$) that couples to charged lepton-neutrino pairs and $h^{+}$ together with the standard Higgs scalar ($\varphi$) can be unified into a Higgs triplet as (${\varphi }^0$, ${\varphi }^{-}$, $h^{+}$)${}^T$. This assignment in turn requires lepton triplets (${\psi }_L^i$) with heavy charged leptons (${\kappa }_L^{+i}$) as the third member: ${\psi }_L^i=({\nu }_L^i,{\ell }_L^i,{\kappa }_L^{+i}{)}^T$, where $i$ ($=1,2,3$) denotes three families. It is found that our model is relevant to yield quasi-vacuum oscillations for solar neutrinos.

Comments: 11 pages, revtex, including 2 figures, accepted for publication in Phys. Rev. D with minor modification of our result