On mixing angles and magnetic moment of heavy tau neutrino

Abstract

If the magnetic moment of unstable tau neutrinos with the mass of $O$(MeV) is in the region of $10^{-8}μ_{B} \lesssim μ_{ν_τ} \lesssim 10^{-6}μ_{B}$, it is compatible with the present experimental and cosmological bounds. It is pointed out here, that if the tau neutrino has such a large magnetic moment and can oscillate into a neutrino of another flavour the results from $νe$ scattering experiment at LAMPF constrain the tau neutrino mixing angles to $sin^{2}2θ_{e τ} \lesssim 2\times 10^{-6} - 2\times 10^{-2}$ and $sin^{2}2θ_{μτ} \lesssim 10^{-6} - 10^{-2}$ depending on the magnetic moment value in the allowed region.