Another Look at Just-So Solar Neutrino Oscillations

Abstract

We take another look at ``Just-So'' solar neutrino oscillations, characterizing them by the energy $E_{\pi/2}$ at which the distance-varying angle is $\pi/2$, instead of the usual $\Delta m^2$. The rising spectrum recently observed by SuperKamiokande is consistent with $E_{\pi/2}\sim$ 6-9 MeV and marginally with 48 MeV. The pp neutrinos must then be reduced to one-half the standard solar model prediction, and $^7$Be neutrinos must make up a significant part of the SAGE and GALLEX gallium signal. For $E_{\pi/2}$ close to 9 and 48 MeV, the $^7$Be neutrinos will also show a large seasonal variation, emphasizing the importance of direct measurements of the $^7$Be neutrinos.