Solar Neutrino Update: Three Detectors Tell Three Stories

For 17 years, a 600‐ton vat of cleaning fluid in the bowels of a South Dakota gold mine was the only detector on Earth looking at neutrinos from the Sun. And what Raymond Davis and his colleagues at the Homestake gold mine reported year after year was very puzzling: Their long‐term average capture rate from 1970 through 1985 was $0.472±0.037$ solar neutrinos captured per day. But the “standard solar model” predicted, with considerable confidence, that the Homestake detector ought to be seeing about 1.8 neutrinos from the Sun per day. Allowing for the uncertainties of the standard solar model, 1.2 captures per day was the very least the theorists would find comprehensible in the light of what they thought they knew about how the Sun works.