Do Two Flavour Oscillations Explain both KamLAND Data and the Solar Neutrino Spectrum?
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The recent measurement of Δsol by the KamLAND experiment with very small errors, makes definitive predictions for the energy dependence of the solar neutrino survival probability Pee. We fix Δsol to be the KamLAND best fit value of 8×10−5 eV2 and study the energy dependence of Pee for solar neutrinos, in the framework of two flavour oscillations and also of three flavour oscillations. For the case of two flavour oscillations, Pee has a measurable slope in the 5–8 MeV range but the solar spectrum measurements in this range find Pee to be flat. The predicted values of Pee, even for the best fit value of θsol, differ by 2–3 σ from the Super-K measured values in each of the three energy bins of the 5–8 MeV range. If future measurements of solar neutrinos by Super-K and SNO find a flat spectrum with reduced error bars (by a factor of 2), it will imply that two flavour oscillations can no longer explain both KamLAND data and the solar spectrum. However a flat solar neutrino spectrum and the Δsol measured by KamLAND can be reconciled in a three flavour oscillation framework with a moderate value of θ13≈13°.
KeywordsSolar neutrino spectrum Neutrino oscilation
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