Just So? Vacuum Oscillations and MSW: An Update

We find that vacuum oscillations (VO), large-mixing-angle and small-mixing-angle MSW solutions to the solar neutrino problem (SNP) give all very good fits to the most recent results. Measurements of the $^7$Be flux can, in some cases, discriminate between different solutions to the SNP; in particular, VO allow $^7$Be fluxes almost as large as the one predicted by the SSM. We find that no evidence for seasonal variations can be extracted from present data, but that the large statistics of SuperKamiokande should make possible to study a significant portion of the presently allowed parameter space by just looking for seasonal variations. We also discuss the Borexino potential for detecting seasonal variations, which looks really impressive.