Supersymmetry, R-parity breaking and the neutrino magnetic moment

We show that supersymmetric theories with R -parity breaking naturally give rise to significant neutrino magnetic moments. In the minimal supersymmetric standard model the transition magnetic moment μ ν e ν μ can be as large as 10 −13 μ B ( μ B is the Bohr magneton). By requiring an SU (2) H horizontal symmetry of the lagrangian in the Yukawa-less limit, μ ν e ν μ may be one order magnitude larger. In this case the main naturalness constraint on the maximum μ ν e ν μ attainable is the electron mass value rather than the bound on the neutrino mass itself.