# From a historical perspective why is beta decay associated with an anti neutrino instead of a neutrino?

I know it sounds like a silly question but didn't both Pauli and Fermi hint at Beta decay missing a particle to carry away a small amount of it's energy or mass but why is this an anti neutrino ?

The neutrino was not actually discovered some years latter so how was the Beta decay dubbed with the anti neutrino?

Only after the neutrino's discovery did we come up with the concept of lepton number (based on the unexpected multiple lepton families), which warranted reclassifying "that other thing emitted in beta emission", which was how we originally defined the word neutrino, as an antineutrino. Ironically, there's still an outside chance the neutrino is its own antiparticle anyway.

• This looks like a great answer, but I hesitate to up-vote it due to the lack of documentation. Do you have any support for (the first part of) this answer? – Rory Daulton Jul 31 '18 at 11:10
• @RoryDaulton For us conceiving of lepton number after neutrinos were discovered? All I can offer is the fact that the neutrino was theorised in 1930, but the muon was unknown until its experimental surprise discovery in 1936. – J.G. Jul 31 '18 at 12:08
• I particularly meant that the "other thing emitted in beta radiation" was originally named the neutrino and was later renamed to the anti-neutrino. – Rory Daulton Jul 31 '18 at 13:26
• see if I get this right...so the anti-neutrino really was named neutrino! But then the lepton numbers were discovered? But what property was garnished that all of a sudden the neutrino is an anti-neutrino? Is it because it vanishes in a burst of energy? What makes it an anti neutrino ? could we just as well call the anti neutrino a neutrino and the neutrino an anti neutrino ...how would we know the difference. "This is history that deserves to be remembered". :-) In quotes because that last sentence I stole from someone else – Sedumjoy Jul 31 '18 at 14:52
• Since the electron's creation is in conjunction with creating a particle of lepton number $-1$, it's natural to consider that an antilepton, and an antiparticle, and an antineutrino. – J.G. Jul 31 '18 at 15:11