This page was prepared at SLAC from a faxed copy of the Official Super-Kamiokande press release. The related release mentioned at the bottom of the page is not available.
Neutrinos are tiny, electrically neutral, sub-atomic particles.
The experiment yields results that are outside the standard theory of particle physics, which describes the fundamental constituents of matter and their interactions. Until now, there has been no firm evidence that neutrinos possess mass. Most of these neutrinos pass through the entire earth unscathed. Faint flashes of light given off by the neutrino interactions in the tank are detected by more than 13,000 photomultiplier tubes that were manufactured for the experiment by Hamamatsu Corporation. The experiment does not determine directly the masses of the neutrinos leading to this effect, but the rate of disappearance suggests that the difference in masses between the oscillating types is very small.