Radiative decays of cosmic background neutrinos in extensions of the MSSM with a vectorlike lepton generation

Abstract

An analysis of radiative decays of the neutrinos ${\ensuremath{\nu}}_{j}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{l}\ensuremath{\gamma}$ is discussed in minimal supersymmetric standard model extensions with a vector like lepton generation. Specifically we compute neutrino decays arising from the exchange of charginos and charged sleptons where the photon is emitted by the charged particle in the loop. It is shown that while the lifetime of the neutrino decay in the Standard Model is $\ensuremath{\sim}{10}^{43}\text{ }\text{ }\mathrm{yrs}$ for a neutrino mass of 50 meV, the current lower limit from experiment from the analysis of the Cosmic Infrared Background is $\ensuremath{\sim}{10}^{12}\text{ }\text{ }\mathrm{yrs}$ and thus beyond the reach of experiment in the foreseeable future. However, in the extensions with a vectorlike lepton generation the lifetime for the decays can be as low as $\ensuremath{\sim}{10}^{12}--{10}^{14}\text{ }\text{ }\mathrm{yrs}$ and thus within reach of future improved experiments. The effect of $CP$ phases on the neutrino lifetime is also analyzed. It is shown that while both the magnetic and the electric transition dipole moments contribute to the neutrino lifetime, often the electric dipole moment dominates even for moderate size $CP$ phases.