A non-resonant dark-side solution to the solar neutrino problem

We reanalyse spin-flavour precession solutions to the solar neutrino problem in the light of the recent SNO CC result as well as the 1258-day Super-Kamiokande data and the upper limit on solar anti-neutrinos. In a self-consistent magnetohydrodynamics approach the resulting scheme has only 3 effective parameters: Deltam(2), muB(perpendicular to) and the neutrino mixing angle theta. We show how a rates-only analysis for fixed muB(perpendicular to) slightly favours spin-flavour precession (SFP) solutions over oscillations (OSC). In addition to the resonant solution (RSFP for short), there is a new non-resonant solution (NRSFP) in the "dark-side". Both RSFP and NRSFP lead to flat recoil energy spectra in excellent agreement with the latest Super-Kamiokande data. We also show that in the presence of a neutrino transition magnetic moment of 10-(11) Bohr magneton, a magnetic field of 80 KGauss eliminates all large mixing solutions other than the so-called LMA solution. (C) 2001 Elsevier Science B.V. All rights reserved.