John Clark (
Tue, 17 Aug 1999 01:57:44 -0400

Hash: SHA1

Joseph C Fineman <> Wrote:

>Antineutrinos exist in any case.

Yes, they were actually discovered experimentally before neutrinos were.

>They are distinguished from neutrinos by their helicity (direction
>of spin relative to their direction of motion). When a neutron decays,
>for example, it yields a proton, an electron, and an antineutrino.
>However, it seems to me that if neutrinos have rest mass, this
>distinction must in principle lapse, since you can then choose a
>frame of reference in which the helicity is reversed.

You can't turn a right hand glove into a left one in any frame of reference, at least not if you stay in 3 dimensions; you'd have to flip it around in the fourth spatial dimension. Besides, the two particles act differently. A antineutrino is absorbed (rarely) by a proton which turns into a neutron and a positron (also called a anti electron), a neutrino is absorbed (rarely) by a neutron which turns into a proton and a electron.

The evidence is starting to look pretty good that the neutrino does have a rest mass although a very tiny one, it's by far the lightest known particle with mass, however there are so many neutrinos they could make up the bulk of the universe.

John K Clark -----BEGIN PGP SIGNATURE-----
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