$SU(3)\otimes U(1)$ Model for Electroweak Interactions

We consider a gauge model based on $SU(3)\otimes U(1)$ symmetry in which the lepton number is violated explicitly by charged scalar and gauge bosons, including a vector field with double electric charge. Although there exist in the literature several models based on a $SU(3)\otimes U(1)$ gauge symmetry, our model has a different representation content and a quite different new physics at an, in principle, arbitrary mass scale. This is possibly the simplest way to enlarge the gauge group $SU_L(2)\otimes U_Y(1)$ in order to have doubly charged gauge bosons, without losing the natural features of the standard electroweak model. The price we must pay is the introduction of exotic quarks, with electric charge $5/3$ and $-4/3$. A previous version of the model was considered several months ago concerning the possibility that in this kind of models neutrinoless double beta decay proceeds even for massless neutrinos and with scalar exchange instead of vector exchange. Our work is in press in Physical Review D.