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From: ethan@utastro.UUCP (Ethan Vishniac)
Newsgroups: sci.astro
Subject: Re: StarDate: October 27 The Amazing Sun
Message-ID: <1375@utastro.UUCP>
Date: Mon, 3-Nov-86 10:11:31 EST
Article-I.D.: utastro.1375
Posted: Mon Nov  3 10:11:31 1986
Date-Received: Tue, 4-Nov-86 05:14:11 EST
References: <1363@utastro.UUCP> <300@prometheus.UUCP> <1369@utastro.UUCP> <592@epimass.UUCP>
Organization: U. Texas, Astronomy, Austin, TX
Lines: 47
Summary: factors of three and such

In article <592@epimass.UUCP>, jbuck@epimass.UUCP (Joe Buck) writes:
> 
>Me:
> >Actually it's almost a factor of three...
> >Nevertheless I would rate the possibility that the sun is turning off
> >as fairly low.  More likely we have some detail about the structure
> >of the core wrong (since we are only sensitive to the high energy
> >tail of the neutrino distribution) or some detail about neutrino
> >physics wrong.  There is a possibility that the electron neutrinos 
> >created in the sun could be converted, with near 100% efficiency
> >into other kinds of neutrinos before leaving the sun.
> 
> Three types of neutrinos are known:  the electron neutrino, the muon
> neutrino, and the tau neutrino.  It is my (possibly confused)
> understanding that if the neutrino has a nonzero rest mass, there
> should be an "oscillation":  the neutrino will interconvert among the
> three types.  This makes the factor of three very interesting.  There
> are some proposals to build muon neutrino detectors; this may shed
> some light on the issue.  
> 
You get the full factor of three this way only through "maximal" mixing,
i.e. if the mixing angles are all equal and large.  This is possible, but
(as I understand it) not particularly likely.  A recent suggestion
is that if neutrinos have small masses and mixing angles then the
order of masses is affected by the presence of a sufficiently dense plasma.
Normally we expect the electron neutrino to be the least massive.
Interactions with the plasma could make it the most massive.  If
the plasma parameters change sufficiently slowly as the neutrino emerges
from the sun then the wave function corresponding to the most massive
neutrino in the core of the sun (electron neutrino) will correspond
to the most massive neutrino in a vacuum (tau neutrino).  It is
possible to get conversion to muon neutrinos instead.  In either
case the detection of neutrinos in our experiments are unlikely
to actually imply anything about neutrinos from the sun.

It would be helpful to see muon neutrinos.  It is somewhat easier
(in fact it's being done now) to look for lower energy neutrinos.
A change in the temperature profile of the sun's core wouldn't
lower the flux of lower energy neutrinos.  Screwy particle physics
would.

-- 
"More Astronomy                Ethan Vishniac
 Less Sodomy"                  {charm,ut-sally,ut-ngp,noao}!utastro!ethan
  - from a poster seen         ethan@astro.AS.UTEXAS.EDU
    at an airport              Department of Astronomy
                               University of Texas