Re: Neutrino & Anti-Neutrino

[John Denker <jsd@MONMOUTH.COM>]

In response to Tony Wayne, at 09:29 AM 3/29/00 -0800, Shapiro, Mark wrote:

> The difference between the neutrino and anti-neutrino is the "helicity",
> which is the projection of the particle spin on its direction of motion.

That's true, but there's another answer that contains an interesting
physics lesson:

Neutrinos are leptons, and they carry lepton number, which is obeys a local
conservation law.

The electron and its neutrino each carry a electronic lepton number of
+1.  In contrast, the positron and the corresponding antineutrino carry an
electronic lepton number of -1.

There are additional categories of lepton number for mu and tau particles.

As a consequence, we can understand why a muon cannot just decay into an
electron;  it must also emit two neutrinos:
        mu -> e + anti-nu_e + nu_mu
so that the electronic and muonic lepton numbers are conserved.