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

Abstract 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 magneto-hydrodynamics approach the resulting scheme has only 3 effective parameters: Δm2, μB⊥ and the neutrino mixing angle θ. We show how a rates-only analysis for fixed μB⊥ 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.