In article <c0g2bg$4lg$1@info4.fnal.gov>, EjP <nospam@hackers.are.bad>

mmeron@cars3.uchicago.edu wrote:

In article <c0eoqe$ctm$3@hood.uits.indiana.edu>,

In article <402ac81f.30314403@news2.aaahawk.com>,
Leon Bronstein <100sparrows@hotmail.com> wrote:

Definitive information on antineutrons seems scarce. I have been

what the half-life of the antineutron is. It looks like physicists

the value is identical to the half-life of the neutron. How sound is

assumption?

Hey, you're right. My Particle Physics Booklet doesn't seem to list

for antineutrons, just neutrons. Electromagnetic and color

seem symmetric under charge conjugation, but the weak force is known to

the bad boy in that regard. Since neutron decay is a weak force
interaction, the antineutron lifetime should be close to the neutron
lifetime, but I couldn't say off the cuff whether it should be equal.

Even the simple half-life of the neutron does not seem all that
firmly established, with error bars around 0.25% of the estimate.

I'm working on it, it's not an easy thing to measure. The lifetime is
long, while at the same time it's hard to just hold on to a chunk of

neutrons.

Since it's hard to confine anti-matter in a stable environment for

study, it seems like our knowledge of antineutrons must be on a

footing than knowledge of neutrons. Even if an antineutron was

lab, would the experimenter know a priori that they have an

it was created by pair production along with a neutron, would there be

way to separate them and know which is which?

Antineutrons should be even harder to measure. Bottle methods must be
right out due to antineutron-nuclear interactions. That leaves the
Penning trap, and the precision obtainable with that method depends on

many neutrons or antineutrons you can send through it. And research
reactors create beams of something around 1e12 neutrons per second,

the number of antineutrinos available to researchers must be quite a

less.

Penning trap relies on charge which is absent here. You've an
magnetic moment but not that much of it. Possibly, in analogy to
Penning trap, some combination of static and time dependent magnetic
fields could trap it, but it would've to have a very low energy for
this.

I thought that, too, but the PDG listed "Penning trap" as
the technique for at least the following lifetime measurement:
J. Byrne, et al., EPL 33 187 (96)

Is this neutron lifetime measurement?

In article <c0g2bg$4lg$1@info4.fnal.gov>, EjP <nospam@hackers.are.bad> writes:

In article <c0eoqe$ctm$3@hood.uits.indiana.edu>,

In article <402ac81f.30314403@news2.aaahawk.com>,
Leon Bronstein <100sparrows@hotmail.com> wrote:

Definitive information on antineutrons seems scarce. I have been wondering
what the half-life of the antineutron is. It looks like physicists assume
the value is identical to the half-life of the neutron. How sound is this
assumption?

Hey, you're right. My Particle Physics Booklet doesn't seem to list stats
for antineutrons, just neutrons. Electromagnetic and color interactions
seem symmetric under charge conjugation, but the weak force is known to be
the bad boy in that regard. Since neutron decay is a weak force
interaction, the antineutron lifetime should be close to the neutron
lifetime, but I couldn't say off the cuff whether it should be equal.

Even the simple half-life of the neutron does not seem all that
firmly established, with error bars around 0.25% of the estimate.

I'm working on it, it's not an easy thing to measure. The lifetime is
long, while at the same time it's hard to just hold on to a chunk of free
neutrons.

Since it's hard to confine anti-matter in a stable environment for long-term
study, it seems like our knowledge of antineutrons must be on a shakier
footing than knowledge of neutrons. Even if an antineutron was created in a
lab, would the experimenter know a priori that they have an antineutron? If
it was created by pair production along with a neutron, would there be any
way to separate them and know which is which?

Antineutrons should be even harder to measure. Bottle methods must be
right out due to antineutron-nuclear interactions. That leaves the
Penning trap, and the precision obtainable with that method depends on how
many neutrons or antineutrons you can send through it. And research
reactors create beams of something around 1e12 neutrons per second, while
the number of antineutrinos available to researchers must be quite a bit
less.

Penning trap relies on charge which is absent here. You've an
magnetic moment but not that much of it. Possibly, in analogy to
Penning trap, some combination of static and time dependent magnetic
fields could trap it, but it would've to have a very low energy for
this.

I thought that, too, but the PDG listed "Penning trap" as
the technique for at least the following lifetime measurement:
J. Byrne, et al., EPL 33 187 (96)

Is this neutron lifetime measurement?

Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"

In article <c0g4r3$rav$2@hood.uits.indiana.edu>,
glhansen@steel.ucs.indiana.edu (Gregory L. Hansen) writes:

In article <6nGWb.17$Y4.6875@news.uchicago.edu>,
<mmeron@cars3.uchicago.edu> wrote:

In article <c0eoqe$ctm$3@hood.uits.indiana.edu>,
glhansen@steel.ucs.indiana.edu (Gregory L. Hansen) writes:

In article <402ac81f.30314403@news2.aaahawk.com>,
Leon Bronstein <100sparrows@hotmail.com> wrote:

My advisor had software set up to
simulate the moderator for the little neutron facility he's building at
Indiana University, so I asked him to try moderating antineutrons, and he
said he didn't even get one antineutron through.

I'm not surprised.

So I think we'd be stuck
with catching decay antiprotons in a Penning trap.

Actually, now that I think about it, there's a Penning trap neutron
lifetime experiment right here, it's been successfully operated and the
bugs shaken out. If we could just get an antineutron source and
antineutron flux monitor,

The problem is that you need a cold source. They're produced hot.
How do you cool them without annihilating them?

"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:402BC8B7.C012DA66@hate.spam.net...

Franz Heymann wrote:

"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:402AE58A.5D33A795@hate.spam.net...

Leon Bronstein wrote:

[snip]

I have been wondering
what the half-life of the antineutron is. It looks like physicists

assume

the value is identical to the half-life of the neutron. How sound

is

this

assumption?

100%, by symmetry. A matter universe could not be told from an
antimatter universe by neutron decay half-life.

Uncle Al seems to have forgotten about the intricacies of the weak
interaction.

Wouldn't make a measurable difference if it made any difference at
all. C and CP violations in particle decay require a severely stacked
deck, as in B or K mesons.

And you are the bloke trying to see if gravity is or is not achiral

Franz Heymann wrote:

"Gregory L. Hansen" <glhansen@steel.ucs.indiana.edu> wrote in message
news:c0epkq$ctm$4@hood.uits.indiana.edu...

[snip]

I looked through a few of the hits for antineutron and lifetime, and
antineutron and half-life, but none seemed to mention a measured lifetime
of the antineutron. What did you find?

The international particle tables make no mention of it. That means it has
never been measured.

There is no way to generate, cool, and confine a sufficent number of
anti-neutrons to make a statistically meaningful measurement. It is
unnecessary by symmetry. If anti-neutrons decayed differently from
neutrons, the Standard Model would go in the trash bin big time.

Confining one or a few anti-hydrogen atoms and looking at spectroscopy
and Lamb Shift are very high priority items. It hasn't been
accomplished. One would be utterly astonished if anything other than
the matter numbers appeared... because the Standard Model would go in
the trash bin big time.

In article <c0fi4f$rnb$1@sparta.btinternet.com>,
Franz Heymann <franz.heymann@btopenworld.com> wrote:

"Gregory L. Hansen" <glhansen@steel.ucs.indiana.edu> wrote in message
news:c0epkq$ctm$4@hood.uits.indiana.edu...

[snip]

I looked through a few of the hits for antineutron and lifetime, and
antineutron and half-life, but none seemed to mention a measured

of the antineutron. What did you find?

The international particle tables make no mention of it. That means it

never been measured.

Well, an experiment that has never been done is one you can't screw up.
You could do the shoddiest job and still be a pioneer.

On Thu, 12 Feb 2004 13:32:49 +0100, Bjoern Feuerbacher
<bfeuerba@ix.urz.uni-heidelberg.de> wrote:

Leon Bronstein wrote:

So where did all the baryons in the universe come from? I thought it

pair production from gamma rays in the early universe, with some slight
"asymmetry" leading to more baryons than anti-baryons.

Well, what was produced in the early universe were quarks, not protons
and neutrons directly. For up, down and strange quarks at least, you
need far less energy for pair production than for protons and neutrons.

Thanks. A lot of physics popular literature gives the impression that

production commonly produces proton/antiproton and neutron/antineutron
pairs, without any hint at quarks. An example is Weinberg's THE FIRST

MINUTES. My searches found many web pages defining pair production and
giving the production of baryons as examples, but never quarks. Is it not

well-understood process? We haven't observed quarks on their own, so I
can't imagine we have a good description of how a bunch of photons
simultaneously produce the required up and down quarks close enough to

other to form a proton or neutron... yet we see baryons produced.