Trying to understand Neutrino Oscillations

Muon-to-Electron Neutrino Oscillations have been observed twice. What causes NO ? If, in practice as opposed to theory, every Quantum system has some spread in Energy [math]\Delta E[/math]; and if such spreads, or "line widths", were wider than the spacings between the "lines" themselves, [math]\Delta E > E_{\nu_{\tau}}-E_{\nu_e}[/math]; then would that explain NO ?? To wit, in practice, it is impossible to produce a "pure mono-chromatic, mono-energetic, mono-flavor" neutrino beam, so that every neutrino manufactured, is inherently some super-position, of the three ever-so-closely-energy-spaced neutrino "flavor" states ??