Solar neutrinos and the Mikheyev-Smirnov-Wolfenstein theory

The observation of solar neutrinos by Kamiokande shows that the solar-neutrino problem cannot be solved by changing the solar model. In combination with the observations with a chlorine detector, it makes the nonadiabatic form of the Mikheyev-Smirnov-Wolfenstein theory most likely, and determines Δm2sin2θ=1.0x10-8 eV2. Probably all neutrinos go through the resonance in the Sun, those from 8B nonadiabatically, all others adiabatically. The latter emerge from the Sun in the higher-mass eigenstate ν2 and have a probability sin2θ to be detected as νe. The gallium experiments, when done with sufficient accuracy, will be able to determine Δm2=m2(νμ)-m2(νe) within fairly close limits. If the day-night effect can be measured, it will further constrain these limits. The small value of Δm2sin2θ explains why the oscillation from νe to νμ has not been observed in the laboratory. From existing experiments, the temperature at the center of the Sun can be determined to be within about 6% of that derived from the standard solar model; future neutrino experiments may determine it to within 1%