Testing the Solar Neutrino Conversion with Atmospheric Neutrinos

TL;DR

This paper investigates how solar neutrino oscillations could cause observable excesses in atmospheric neutrino data, providing specific energy and zenith angle signatures consistent with SuperKamiokande observations.

Contribution

It presents a detailed analysis of neutrino oscillation effects on atmospheric neutrino events, highlighting distinctive energy-dependent signatures that can confirm solar neutrino conversion.

Findings

Observable excess of e-like events up to 12% in sub-GeV samples.

Strong zenith angle dependence of excess at high energies.

Agreement of predicted excess properties with SuperKamiokande data.

Abstract

Neutrino oscillations with parameters relevant for the large mixing solution of the solar neutrino problem ($\Delta m^2_{21} = (2 - 20) \cdot 10^{-5}$ eV$^2$, $\sin^2 2\theta_{12} > 0.65$) can lead to observable (up to 10 - 12 %) excess of the e-like events in the sub-GeV atmospheric neutrino sample. The excess has a weak zenith angle dependence in the low energy part of the sample and strong zenith angle dependence in the high energy part. The effect rapidly decreases with energy of neutrinos, it is suppressed in the multi-GeV sample. These signatures allow to disentangle the effect from other possible explanations of the excess. The possibility of change of the sign of the up-down asymmetry of the excess with energy (positive in the sub-GeV region and negative in the multi-GeV region) is marked. The predicted properties of excess are in agreement with SuperKamiokande data.