# Neutrino flavor eigenstate interaction with matter

We know that neutrino eigenstates are not mass eigenstate and this therefore produces neutrino oscillations. This is, however, deduced from the fact that the neutrino of one flavor produces the corresponding partner lepton of the same flavor (electron neutrino only produces electrons, etc.).

My question is : how do we know that this is indeed the case experimentally?

I know that the standard model predicts that it is the case, but how can we verify that, if the only way to tell that there was a neutrino of a given flavor is to detect the corresponding partner ?

EDIT : To give some precision about the kind of answer I'd like :

Saying : we know the flavor of a neutrino by the lepton it produces is not enough. In that case, we could imagine that a lepton does not always produces the corresponding neutrino (say, an "electronic neutrino" is by definition a neutrino that creates electrons when it interacts with a nucleon, but we could imagine that an electron could produce half of the time a "muonic neutrino" (always producing muons) and half of the time an "electronic neutrino"). I know that's not what predicts the standard model, but has it been verified experimentally ? If so, how can we do that, as we don't know what is produced before detecting it...

I ask that because we could imagine that it could be another way to "explain" at least part of the neutrino oscillations physics.

This is what we mean by the flavor state of a neutrino.

A neutrino which is involved in a weak interaction with a charged lepton has the same flavor as the charged lepton. By definition.

The observation of a charged partner is the operator for neutrino flavor measurement.

• Instead of assuming neutrino oscillations, we could imagine that the creation of neutrino is not the same than their annihilation. How do we prove experimentally that this is always the case. Or I state it the other way around : if I know the flavor of a neutrino by the partner it produces, how do I know that the partner always produces the corresponding flavor. Is there an experimental fact to say that ? I'll edit my question.