There is positive experimental evidence for an electron neutrino associated with the electron and a muon neutrino associated with the muon. Theory suggests that there should be a third, the tauon neutrino , associated with the tauon.
Neutrinos are leptons .
All are very elusive, travelling at the speed of light and passing through matter with virtually no interaction. The New Penguin Dictionary of Science 2. K capture The New Penguin Dictionary of Science 5. All rights reserved.