Re: Neutrino & Anti-Neutrino

[Leigh Palmer <palmer@SFU.CA>]

> On Wed, 29 Mar 2000, 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.  As
> > I recall (I've got a 50-50 chance of being correct on this one), the
> > neutrino has a left-handed helicity while the anti-neutrino has a
> > right-handed helicity.
>
> Hmm ...  If neutrinos have mass, does this mean that one person's neutrino
> is another person's antineutrino and, therefore, that one person's beta-
> decay is another person's beta+ decay?

The argument used to be that there is no frame of reference in which
a neutrino looks like an antineutrino. Therefore neutrinos must
propagate with the speed of light, and therefore they must be massless.
Luis Alvarez told me that. It's difficult to shake the idea that it
might be true, but they say you can't stop progress. In this case that
involves discarding a perfectly serviceable quantum number.

Leigh