On nondiagonal neutral neutrino currents

The electroweak theory predicts diagonal neutrino neutral currents. Possible experimental tests of this prediction are discussed. The upper limits on the coupling constants of nondiagonal neutral neutrino currents are obtained making use of scarce νsub(eiesup(-) and anti ν sub(e)e-scattering data and of extremely low upper limit on the μ→3e decay probability. Further restraints on nondiagonal neutrino couplings may be obtained measuring the cross section of the process ν sub(μ) → ν sub(μ)μsup(+)μsup(-) in the Coulomb field of a iucleus and improving the upper limits on the tau → 3e, tau → 3μ, tau → 2eμ, and tau → 2μe decay probabilities. It should be emphasized that this interpretation of experimental data under consideration is possible only in terms of a nonrenormalizable internally selfiinconsistent theoretical scheme