Constraints on Neutrino Lifetime from the Sudbury Neutrino Observatory

Abstract: The long baseline between the Earth and the Sun makes solar neutrinos an excellent test beam for exploring possible neutrino decay. The signature of such decay would be an energy-dependent distortion of the traditional survival probability which can be fit for using well-developed and high precision analysis methods. Here a model including neutrino decay is fit to all three phases of $^8$B solar neutrino data taken by the Sudbury Neutrino Observatory. This fit constrains the lifetime of neutrino mass state $\nu_2$ to be ${>8.08\times10^{-5}}$ s/eV at $90\%$ confidence. An analysis combining this SNO result with those from other solar neutrino experiments results in a combined limit for the lifetime of mass state $\nu_2$ of ${>1.04\times10^{-3}}$ s/eV at $99\%$ confidence.