, Volume 50, Issue 5, pp 1515-1521
Date: 08 Jan 2011

Do Two Flavour Oscillations Explain both KamLAND Data and the Solar Neutrino Spectrum?

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The recent measurement of Δ sol by the KamLAND experiment with very small errors, makes definitive predictions for the energy dependence of the solar neutrino survival probability P ee . We fix Δ sol to be the KamLAND best fit value of 8×10−5 eV2 and study the energy dependence of P ee for solar neutrinos, in the framework of two flavour oscillations and also of three flavour oscillations. For the case of two flavour oscillations, P ee has a measurable slope in the 5–8 MeV range but the solar spectrum measurements in this range find P ee to be flat. The predicted values of P ee , even for the best fit value of θ sol , 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 Δ sol measured by KamLAND can be reconciled in a three flavour oscillation framework with a moderate value of θ 13≈13°.