Seasonal variations of the7Besolar neutrino flux

Measuring the ${}^7\mathrm{Be}$ solar neutrino flux is crucial towards solving the solar neutrino puzzle. The Borexino experiment, and possibly the KamLAND experiment, will be capable of studying the ${}^7\mathrm{Be}$ neutrinos in the near future. We discuss (1) how the seasonal variation of the Borexino and KamLAND data can be used to measure the ${}^7\mathrm{Be}$ solar neutrino flux in a background independent way and (2) how anomalous seasonal variations might be used to discover vacuum neutrino oscillations, independent of the solar model and the measurement of the background. In particular, we find that, after three years of Borexino or KamLAND running, vacuum neutrino oscillations can be either established or excluded for almost all values of $({\sin }^{2}2\theta ,\Delta m^2)$ preferred by the Homestake, GALLEX, SAGE, and Super-Kamiokande data. We also discuss how well seasonal variations of the data can be used to measure $({\sin }^{2}2\theta ,\Delta m^2)$ in the case of vacuum oscillations.