Re: Would an anti-neutron stick to a proton via the strong force?

John,

It is true that neutrons and antineutrons have the same mass, charge,
spin, and lifetime.  It is also true that neutrons and antineutrons 
have equal magnitude and oppositely directed magnetic dipole moments,
but I would resist saying that "an antineutron is just like a neutron"
because these two objects have completely different quark content.
A neutron contains two down and one up valence quarks, while an
antineutron contains two antidown and one antiup valence antiquarks.
The neutron is a baryon while the antineutron is an antibaryon.

Now for your question, "So, could an antineutron participate in 
forming a normal atomic nucleus?"  No, it can not.  A proton's
valence quark content is two up quarks and one down quark.
If a proton and an antineutron get close enough, an up quark from the
proton will very quickly (in less than a billionth of a billionth of a
second for an interaction mediated by the strong force) annihilate
with an antiup antiquark from the antineutron, or a down quark from
the proton will annihilate with an antidown antiquark from the
antineutron with the same result.  The combination proton plus
antineutron is not stable.

See one of my previous responses on the nonexistent "unmatter"
http://madsci.org/posts/archives/2005-07/1120397918.Ph.r.html

Your other questions are probably moot now, but they are answerable.
"...would they stick to protons?  After all, the pions are the same,
so would it be attracted to other nucleons, or be repelled by them...?"

You know that a proton and a neutron will bind to form a deuteron,
the nucleus of deuterium or heavy hydrogen (which is stable).  But
two protons will not bind together.  You might think this is because
of their electrical repulsion, but that's only part of the problem.
Neutrons are electrically neutral but even two neutrons will not
bind together despite the fact that they exchange pions.

The answer lies in a concept called "isospin".  Particles with
opposite isospin will bind; particles with the same isospin will not:
  proton  (+1/2) and neutron (-1/2) will bind;
  proton  (+1/2) and proton  (+1/2) will not bind;
  neutron (-1/2) and neutron (-1/2) will not bind;
so now you can see
    proton  (+1/2) and antineutron (+1/2) will NOT bind.


Here are some resources to explore:
http://en.wikipedia.org/wiki/Neutron
http://en.wikipedia.org/wiki/Antineutron
http://en.wikipedia.org/wiki/Nuclear_magneton
Review of Particle Physics by the Particle Data Group
  http://pdg.lbl.gov/
  http://pdg.lbl.gov/2005/tables/contents_tables.html
  http://pdg.lbl.gov/2005/tables/bxxx.pdf
Introduction to Elementary Particles by David Griffiths ISBN 0-471-60386-4


--Dr. Randall J. Scalise  
http://www.phys.psu.edu/~scalise/