The Oscillation Length Resonance in the Transitions of Solar and Atmospheric Neutrinos Crossing the Earth Core

Abstract

The characteristic features of the neutrino oscillation length resonance, taking place in the $\nu_2 \to \nu_{e}$ and $\nu_{\mu} \to \nu_{e}$ ($\nu_e \to \nu_{\mu (\tau)}$) transitions in the Earth of the solar and atmospheric neutrinos crossing the Earth core, are reviewed. The resonance enhances dramatically these transitions at small mixing angles but differs from the MSW one. It can be responsible, e.g., for the small excess of e-like events at Zenith angles $\theta_{z} \sim (130^{\circ} - 180^{\circ})$ and can produce at least part of the Zenith angle dependence of the rate of $\mu-$like events, exhibited by the Super-Kamiokande atmospheric neutrino data.