For the first time, physicists have confirmed that certain subatomic particles have mass and that they could account for a large proportion of matter in the universe, the so-called dark matter that astrophysicists know is there but that cannot be observed by conventional means.
The finding concerns the behavior of neutrinos, ghost-like particles that travel at the speed of light. In the new experiment, physicists captured a muon neutrino in the process of transforming into a tau neutrino.
Researchers had strongly believed that such transformations occur because they have been able to observe the disappearance of muon neutrinos in a variety of experiments.
But the research announced Monday marks the first time that the appearance of a tau neutrino has been directly observed.