Vacuum oscillations and excess of high energy solar neutrino events observed in Superkamiokande

TL;DR

This paper proposes that vacuum oscillations of solar neutrinos can explain the observed high-energy excess in Superkamiokande data, predicting seasonal variations in neutrino flux as a key signature.

Contribution

It introduces a vacuum oscillation solution to the Solar Neutrino Problem that accounts for high-energy neutrino excess and predicts seasonal flux variations.

Findings

Vacuum oscillation solution fits observed high-energy neutrino spectrum.

Predicted seasonal variation of Be7 neutrino flux as a signature.

Future detectors can test the seasonal variation hypothesis.

Abstract

The excess of solar-neutrino events above 13 MeV that has been recently observed by Superkamiokande can be explained by the vacuum oscillation solution to the Solar Neutrino Problem (SNP). If the boron neutrino flux is 20% smaller than the standard solar model (SSM) prediction and the chlorine signal is assumed 30% (or 3.4 sigmas) higher than the measured one, there exists a vacuum oscillation solution to SNP that reproduces both the observed spectrum of the recoil electrons, including the high energy distortion, and the other measured neutrino rates. The most distinct signature of this solution is a semi-annual seasonal variation of the Be7 neutrino flux with maximal amplitude. While the temporal series of the GALLEX and Homestake signals suggest that such a seasonal variation could be present, future detectors (BOREXINO, LENS and probably GNO) will be able to test it.