Solar-neutrino experiments

The observation of solar neutrinos at Kamiokande rules out the Mikheyev-Smirnov-Wolfenstein (MSW) theory with a ‘‘large’’ mass difference between the neutrinos, Δ${\mathrm{m}}^2$≃${10}^{\mathrm{-}4}$ ${\mathrm{eV}}^2$. There remain the MSW theory with a small Δ${\mathrm{m}}^2$≃${10}^{\mathrm{-}7}$ ${\mathrm{eV}}^2$ or the assumption of unexpectedly low central temperature in the Sun. A decision between these two alternatives will be possible on the basis of the future gallium experiment, and the Sudbury experiment with heavy water.