Lepton-number violation with quasi-Dirac neutrinos

We investigate lepton-number violation in weak interactions with massive Dirac neutrinos. In the framework of a simple SU(3)L×U(1) electroweak model we find that neutrinos naturally acquire only Dirac masses at tree level, and for an odd number of lepton families, one neutrino remains massless. After a spontaneous breakdown of symmetry we find that the SU(2)×{}U(1) effective theory has lepton-number-violating currents which couple to the standard gauge bosons. Flavorconserving |Δl|=2 processes such as neutrinoless double-β decay are forbidden in the simplest model, but processes such as μ^-+(A, Z)→e⁺+(A, Z-2) and K^-→π⁺e^-μ^- are allowed.