Another look at “just-so” solar neutrino oscillations

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