Experimental tests of the Mikheyev-Smirnov-Wolfenstein effect

The fundamental nature of the hypothesis of a nonzero neutrino mass and mixing makes it imperative that confirmation be sought for this as a solution to the solar neutrino problem. While observable effects for the most probable values of the parameters Δ${\mathit{m}}^2$ and ${\sin }^2$(2θ) can be large, in general they are not. Regeneration of the solar neutrino signal itself in the Earth is the most promising possibility. Specific orientations of the Sun and Earth give maximum effects. 20% to 30% modulation of the signal is typical for some portion of the solar neutrino flux itself. In some cases the effect can be much greater. In general, for most night observing times, the regeneration effect can be damped. Specific selection of peak sensitivity depends on the parameters Δ${\mathit{m}}^2$ and ${\sin }^2$(2θ), the location of the detector, and the time of night.