Livescience has an article on a recent test shot of a beam of neutrinos from Fermi-lab (in Batavia, IL) to a particle detector in Soudan, MN. As a result of some of the neutrinos not making it, the scientists have apparently verified a theory which indicates neutrinos have mass. This sets up further studies into the nature of neutrinos.
There are three types of neutrinos, each associated with a different charged particle: the electron neutrino, the muon and the tau. The Fermi scientists think the vanishing act they witnessed was a result of the neutrinos changing from one form to another, a phenomenon called “neutrino oscillation.”
The test results provide further evidence that neutrinos must have mass, the scientists say. If the masses of all three types were zero, neutrino oscillation would not occur.