Limits on $ν_μ(ν_{e}) \to ν_τ$ oscillations and tau neutrino magnetic moment from neutrino-electron scattering

Abstract

The combined effect of neutrino flavor oscillations and neutrino magnetic moment on neutrino-electron scattering is discussed. It is shown, that if the tau neutrino has a (large) magnetic moment and can oscillate into a neutrino of another flavor it can be used for a sensitive search for $ν_μ(ν_{e}) \to ν_τ$ neutrino oscillations and the tau neutrino magnetic moment in neutrino -electron scattering experiments. The combined limits on the mixing angles and the tau neutrino magnetic moment $sin^{2}2θ_{μτ}\times μ_{ν_τ}^{2} < 1.1 \times 10^{-18}μ_{B}^{2}$ and $sin^{2}2θ_{eτ}\times μ_{ν_τ}^{2} < 2.3 \times 10^{-18}μ_{B}^{2}$ for $Δm^{2} > 10~ eV^{2}$ are presented based on results of a study of the neutrino-electron elastic scattering at LAMPF. For $ν_μ\to ν_τ$ oscillations, this would results in sensitive limit of $sin^{2}2θ_{μτ} < 4 \times 10^{-6}$, assuming the tau neutrino magnetic moment being equal to the present experimental limit of $5.4 \times 10^{-7} μ_{B}$. The tau neutrino magnetic moment would be constrained to $μ_{ν_τ} < 1.0 \times 10^{-8} μ_{B}$, assuming the existence of $ν_μ\to ν_τ$ oscillations with the mixing angle $sin^{2}2θ_{μτ}$ equal to the present experimental limit of 0.01 for $Δm^{2} > 10~ eV^{2}$.\ Under similar assumptions the corresponding limits for $ν_{e}\to ν_τ$ oscillations could be set to $sin^{2}2θ_{eτ} < 8 \times 10^{-6}$ and $μ_{ν_τ} < 3.9 \times 10^{-9}μ_{B}$.