Nonuniversal neutral currents ofνeandνμ

The present status and the general consequences of a violation of ${\nu }_e-{\nu }_{\mu }$ universality in weak neutral currents are examined from a phenomenological point of view. If $\xi$ is the strength of the ${\nu }_e$ coupling relative to the ${\nu }_{\mu }$ coupling, an analysis of the available data gives two possible values: $\xi =1.45\mathrm{}\pm 0.2 \mathrm{and} -0.6\mathrm{}\pm 0.2$. A measurement of the total cross section $\sigma \left({\nu }_{e}e\right)$ would reveal the deviations of $\xi$ from unity much more easily than the measurement of $\sigma \left({\overline{\nu }}_{e}e\right)$. The effects of nonuniversality on neutrino cross sections when the ${\nu }_e$ undergoes flavor oscillations in vacuum are studied. A sizable nonuniversality will facilitate the observation of matter effects on the neutrino oscillations.