Large mixing angle solution to the solar neutrino problem and random matter density perturbations

There are reasons to believe that mechanisms exist in the solar interior which lead to random density perturbations in the resonant region of the Large Mixing Angle solution to the solar neutrino problem. We find that, in the presence of these density perturbations, the best fit point in the (sin22θ,Δm2) parameter space moves to smaller values, compared with the values obtained for the standard LMA solution. Combining solar data with KamLAND results, we find a new compatibility region, which we call very-low LMA, where sin22θ≈0.6 and Δm2≈2×10−5 eV2, for random density fluctuations of order 5%<ξ<8%. We argue that such values of density fluctuations are still allowed by helioseismological observations at small scales of order 10–1000 km deep inside the solar core.