system
Given the following post, respond as if you're commenting on Reddit:
human
What's the experimental evidence for neutrino flavours?

How do we know there are different neutrino flavours and that there are only 3? How can a detector tell the difference between muon neutrinos and electron neutrinos? I'm a final year undergraduate and know a reasonable amount of particle physics in general, so feel free to get technical. Every time I google this I just get stuff about neutrino oscillations instead.
gpt
Well the flavours have to do with the lepton flavours they're coupled to. A W boson couples electrons and anti-electron neutrinos, muons and anti-muon neutrinos and so on. If the neutrino collides and produces an electron or positron, then the electron-flavoured component is the state measured in the collision. If a muon/anti-muon produced, then the collision measured the muon-flavoured component.

It's hard to speak of it being an 'electron neutrino' *per se* because that flavour component is only relevant when the interacts in some collision/interaction. While it's in flight, it's a superposition of states, and so we can only speak of future interactions with regards to which flavour component is the component that gets measured (much like how an electron is measured to have spin up or down, but in flight prior to the interaction is both)