# Why are the neutrino flavour eigenstates and mass eigenstates different?

Why does this happen for neutrinos and not for say, electrons and muons. Is there some way to predict which particles might oscillate amongst their flavour and which won't?

For the charged leptons this is not the case. For an electron to turn into a Tau it needs a lot of energy. Consider a beam of e- with an energy just above the $\tau$- rest mass and along its path some of the e- turn into $\tau$- The other e- would quickly overtake and the distance between the particles would be huge. This makes it difficult to get a coherent state.