Solar Neutrinos: Interpretation of Results

Abstract

Recent SNO results give strong evidence that the solar neutrinos undergo the flavor conversion. Main issue now is the identification of the mechanism of conversion. The LMA MSW solution with $Δm^2 = (5 - 7) \cdot 10^{-5}$ eV$^2$, $\tan^2 θ= 0.35 - 0.45$ looks rather plausible: it fits well the experimental data and our new theoretical prejudices. In the LMA case, KamLAND should see (0.5 - 0.7) reduced signal. VAC-QVO and LOW are accepted at about $3σ$-level. The SMA solution is practically excluded. No sub-leading effects produced by $U_{e3}$ and admixture of sterile neutrino have been found. The fit becomes worse with increase of $U_{e3}$ (for LMA) and the $ν_s$ admixture. Still (30 - 50)% presence of the sterile neutrino is allowed. Solutions based on the neutrino spin-flip in the magnetic fields of the Sun as well as on non-standard neutrino interactions give good fit of the data. If KamLAND confirms LMA MSW, the spin-flip and non-standard interactions can be considered (and will be searched for) as sub-leading effects.