We now know that neutrinos have masses and that the flavor eigenstates (νelectron, νmuon, νtau ) are not the mass eigenstates (ν1, ν2, ν3).
This means that an electron muon is a quantum mechanical mixture of different masses and a neutrino that has a definite mass is a quantum mechanical mixture of the different flavors (electron, muon, tau).
Gack.
