Limits on ${\nu }_{\mu }({\nu }_e)\to {\nu }_{\tau }$ 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 ${\nu }_{\mu }({\nu }_e)\to {\nu }_{\tau }$ 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 $si{n}^{2}2{\theta }_{\mu \tau }\times {\mu }_{{\nu }_{\tau }}^2<1.1\times 10^{-18}{\mu }_B^2$ and $si{n}^{2}2{\theta }_{e\tau }\times {\mu }_{{\nu }_{\tau }}^2<2.3\times 10^{-18}{\mu }_B^2$ for $\Delta m^2>10e{V}^2$ are presented based on results of a study of the neutrino-electron elastic scattering at LAMPF. For ${\nu }_{\mu }\to {\nu }_{\tau }$ oscillations, this would results in sensitive limit of $si{n}^{2}2{\theta }_{\mu \tau }<4\times 10^{-6}$, assuming the tau neutrino magnetic moment being equal to the present experimental limit of $5.4\times 10^{-7}{\mu }_B$. The tau neutrino magnetic moment would be constrained to ${\mu }_{{\nu }_{\tau }}<1.0\times 10^{-8}{\mu }_B$, assuming the existence of ${\nu }_{\mu }\to {\nu }_{\tau }$ oscillations with the mixing angle $si{n}^{2}2{\theta }_{\mu \tau }$ equal to the present experimental limit of 0.01 for $\Delta m^2>10e{V}^2$.\ Under similar assumptions the corresponding limits for ${\nu }_e\to {\nu }_{\tau }$ oscillations could be set to $si{n}^{2}2{\theta }_{e\tau }<8\times 10^{-6}$ and ${\mu }_{{\nu }_{\tau }}<3.9\times 10^{-9}{\mu }_B$.

Comments: 6 pages, 2 figures, Latex. The paper is extended to the analysis of combined effects of tau neutino magnetic moment and ${\nu }_e\to {\nu }_{\tau }$ oscillations from the LAMPF neutrino-electron scattering experiment