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From: jonab@sdcrdcf.UUCP
Newsgroups: net.physics
Subject: Re:  Particle Mass
Message-ID: <793@sdcrdcf.UUCP>
Date: Mon, 23-Jan-84 12:07:09 EST
Article-I.D.: sdcrdcf.793
Posted: Mon Jan 23 12:07:09 1984
Date-Received: Fri, 27-Jan-84 08:41:16 EST
References: <15829@sri-arpa.UUCP>
Reply-To: jonab@sdcrdcf.UUCP (Jonathan Biggar)
Organization: System Development Corporation, Santa Monica
Lines: 20

In article <15829@sri-arpa.UUCP> gwyn%brl-vld@sri-unix.UUCP writes:
>
>Apart from the probability that the proper mass of a neutrino is 0,
>

This is not necessarily true.  The best that particle physicists can
tell is that the mass of the neutrino is very small, on the order
of < 10 eV.  This can happen because of the Heisenburg Uncertainty
Principle, which can be interpreted to say that conservation of
mass-energy can be violated as long as the violation occurs
for a short enough period of time.  I also recall that several
of the Grand Unified Field theories actually predict that neutrinos
have a small but real rest mass.  Considering that the smallest
massed particle that we know to exist so far is the electron, and
its mass is ~ .5 MeV, the < 10 eV mass of the neutrino may well
be beyond our means of measuring yet.
-- 
Jon Biggar
{allegra,burdvax,cbosgd,hplabs,ihnp4,sdccsu3,trw-unix}!sdcrdcf!jonab