Close but not quite . <| sep |> I believe the question is how I would do it . <| sep |> No tuo nyt ainakin oli kuin lynti vasten kasvoja . <| sep |> Is there a possible mechanism for neutrino oscillations or lepton numbers aren ' t persistent for neutrinos and are just bad quantum numbers . The fact that neutrinos have mass already tells you that the flavour is not a consevred quantity unless there would be a special smmetry that alignes flavour and mass eigenstates , but that is kind of irrelevant . Perhaps lepton numbers are conserved at weak vertices but during free particle propagationyes that is pretty much it . Neutrinos will evolve according to the mass basis and thus the flavour can change over macroscopic distances . Had kaons been notoriously difficult to observe , its decay would look like a strange quark oscillates into a down quark , rather than the quark changing flavours at the decay vertex . The meson systems are very different to neutrinos . In the case of neutrinos you will find 3 mass eigenstates that are coherent superpositions of the flavours . A neutral Kaon for example antid s will be a pure flavour and a pure mass state . Similarly , atm its difficult to prove whether the neutrino actually changed flavour midflight or was already a different flavour from its emitted pair . For a single neutrino this is of course impoissible to show , but for an ensemble this is done in neutrino oscillation experiments . At production you will create a neutrino beam that consists almost only of neutrinos of one flavour . At the detection target a few 100 km away from that you can show tht the detected beam has changed its flavour compostion . Another i think even more appealing evidence is the sun . Neutrinos in the sun are predominantly produced b hydrogen fusion and thus in electron flavour . However at earth you detect solar neutrinos in all flavours .