But if both it and the explanation for the solar-neutrino deficit were true, there would have to be a fourth sort of neutrino one which its proponents refer to as a sterile neutrino.

ECONOMIST: Neutrinos

Besides being a useful source of dark matter, it may explain the solar-neutrino deficit (the gap between prediction and observation would be caused by a different mutation, from electron neutrinos into undetectable tau neutrinos).

ECONOMIST: Neutrinos

One explanation for the solar-neutrino deficit (only a third of the predicted number have been detected) is that electron-neutrinos produced by nuclear-fusion reactions in the sun's core mutate into the other two types, which are harder to detect.

ECONOMIST: The news that neutrinos have mass is both good and bad