6533b861fe1ef96bd12c455c

RESEARCH PRODUCT

Lepton-number violation with quasi-Dirac neutrinos

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description

We investigate lepton-number violation in weak interactions with massive Dirac neutrinos. In the framework of a simple $\mathrm{SU}{(3)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1)$ 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)\ifmmode\times\else\texttimes\fi{}U(1) effective theory has lepton-number-violating currents which couple to the standard gauge bosons. Flavorconserving $|\ensuremath{\Delta}l|=2$ processes such as neutrinoless double-$\ensuremath{\beta}$ decay are forbidden in the simplest model, but processes such as ${\ensuremath{\mu}}^{\ensuremath{-}}+(A, Z)\ensuremath{\rightarrow}{e}^{+}+(A, Z\ensuremath{-}2)$ and ${K}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{e}^{\ensuremath{-}}{\ensuremath{\mu}}^{\ensuremath{-}}$ are allowed.