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 DELTA-m2sin2-theta = 1.0 X 10(-8) eV2. Probably all neutrinos go through the resonance in the Sun, those from B-8 nonadiabatically, all others adiabatically. The latter emerge from the Sun in the higher-mass eigenstate nu-2 and have a probability sin 2-theta to be detected as nu(e). The gallium experiments, when done with sufficient accuracy, will be able to determine DELTA-m2 = m2(nu(mu)-m2(nu(e)) within fairly close limits. If the day-night effect can be measured, it will further constrain these limits. The small value of DELTA-m2sin2-theta explains why the oscillation from nu(e) to nu(mu) 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%.