Large neutrino magnetic dipole moments in MSSM extensions

Abstract

An analysis of the Dirac neutrino magnetic moment with standard model interactions gives ${\ensuremath{\mu}}_{\ensuremath{\nu}}\ensuremath{\sim}3\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}19}{\ensuremath{\mu}}_{B}({m}_{\ensuremath{\nu}}/1\text{ }\text{ }\text{eV})$. The observation of a significantly larger magnetic moment will provide a clear signal of new physics beyond the standard model. The current experimental limits on the neutrino magnetic moments are orders of magnitude larger than the prediction with the standard model interactions and thus its test appears out of reach. Here we give an analysis of the Dirac neutrino magnetic moments within the framework of a minimal supersymmetric standard model extension with a vectorlike lepton generation. Specifically we compute the moments arising from the exchange of $W$ and the charged leptons in the loop, as well as from the exchange of charginos, charged sleptons and charged mirror sleptons. It is shown that the neutrino moment in this case can be several orders of magnitude larger than the one with standard model-like interactions, lying close to and below the current experimental upper limits and should be accessible in an improved future experiment. A correlated prediction of the heaviest neutrino lifetimes from radiative decays to the lighter neutrinos via exchange of charginos and sleptons in the loops is also made. The predicted lifetimes are several orders of magnitude smaller than the one with the standard model interactions and also lie close to the current experimental limits from analyses using the cosmic background neutrino data.