Neutrino quick-change artist caught in the act

Transformation from muon to tau confirms the elusive particles have mass

In a truly transformative event, physicists have for the first time found direct evidence that a neutrino, a ghostly elementary particle that barely interacts with matter, morphs from one type into another. The finding, announced May 31 in a news release, provides additional support for the notion that neutrinos have mass, a property that requires an explanation beyond the realm of the standard model of particle physics.