Why aren't neutrino oscillations averaged out by incoherence?

Question

Electromagnetic oscillations that have incoherent sources do not manifest any oscillatory or interference patterns. Only when the sources are distilled by appropiate filters like prisms is the oscillation nature of the field observationally manifest

Neutrinos sourced from the sun are presumably being emitted with no spatial or temporal correlations, hence the source should be considered incoherent. Nonetheless, flavor oscillations are observed and in fact are the currently accepted explanation to the Solar neutrino problem

Question:

Why is it that the incoherent solar sources does not average out oscillations and just result in averaged neutrino intensities?

Answer 1

Perhaps I'm wrong in this, and would appreciate correctives from experimental colleagues; but, for solar neutrinos, one does not see actual oscillatory signals. One observes depletion of $\nu_e$s, i.e., one observes ~ 30% of the $\nu_e$s produced in the sun, in Charged Current weak interactions; but, importantly, at the same time, full intensity for the sum $\nu_e+\nu_\mu+\nu_\tau$ in Neutral Current interactions, the A.B. McDonald NP of 2015 for the decisive SNO experiment.

The conclusion is that 2/3 of the electron neutrinos produced in the sun have converted to neutrino flavors undetectable by CC interactions on earth. The actual wiggling of the oscillation formula is too much to expect, given the broad range of energies, distances travelled, and MSW resonant conversions of solar electrons involved in the solar models. What reaches the earth is thus averaged depleted intensities for $\nu_e$ and, oh the joy!, matching enhanced intensities of uninvited $\nu_\mu+\nu_\tau$ s.

A neutrino produced in a solar nuclear reaction only interferes with itself, which entails its 3 mass eigenstate components, and not other neutrinos, of course. It is these three components in the wave packet of each neutrino separately that interfere with each other as they interact with the electrons of the MSW resonant conversion medium and then zip for 8 minutes in vacuum until the reach the detector of their doom on earth.

I don't see the point in perorating on energy dependencies and variations of oscillation cycles involved, etc... But the essence of your punchline question is that, indeed, what reaches us is aggregate bulk intensities, composed of umptillions of neutrinos incoherent w.r.t. each other, but coherent within their individual wave packets, until detected.

Answer 2

They do average by incoherence ! This is precisely the reason for which one sees only 1/3 of the neutrinos leaving the sun as electron neutrinos. Average indeed.