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| EdV... |
 Posted: Fri Oct 16, 2009 6:36 am |
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I remember in high school physics reading that when an electron and an
anti-electron meet they yield two gamma particles.
My question:
What happens to the kinetic energy of the two particles? Does it show
up in the wavelength of the two gamma particles? Or is the kinetic
energy represented in a different particle?
I was going to post this to sci.physics.particle but that site looked
a little . . . scary . . . I guess.
Thanks much,
EdV |
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| Tom Roberts... |
| Posted: Fri Oct 16, 2009 9:20 am |
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EdV wrote:
[quote:451bba62c7]I remember in high school physics reading that when an electron and an
anti-electron meet they yield two gamma particles.
[/quote:451bba62c7]
Hmmmm. The annihilation of e+ and e- can yield any number of gammas >= 2,
depending on the details of how the annihilation process occurs. But 2 is by far
the most likely number of gammas emitted.
Note that it is possible to create a bound state of e+ e- called positronium,
and it can have a rather long lifetime. But it eventually annihilates into 2 or
more gammas; "eventually" is within a few microseconds at most, and is usually
much shorter than that.
[quote:451bba62c7]What happens to the kinetic energy of the two particles?
[/quote:451bba62c7]
The total energy of the incident e+ and e- is shared among all of the outgoing
gammas. This of course includes their kinetic energy.
[quote:451bba62c7]Does it show
up in the wavelength of the two gamma particles?
[/quote:451bba62c7]
The energy of a gamma is proportional to its frequency, and is thus inversely
proportional to its wavelength.
Tom Roberts |
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| Uncle Al... |
| Posted: Fri Oct 16, 2009 12:58 pm |
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EdV wrote:
[quote:38245d8823]
I remember in high school physics reading that when an electron and an
anti-electron meet they yield two gamma particles.
[/quote:38245d8823]
Or three. Two from fast singlet positronium annihalation, three from
slower triplet; and you also have direct annihalation without
intermediate positronium formation.
[quote:38245d8823]My question:
What happens to the kinetic energy of the two particles? Does it show
up in the wavelength of the two gamma particles? Or is the kinetic
energy represented in a different particle?
[/quote:38245d8823]
Kinetic energy shows up in the energies of the gamma photons depending
on the observer's point of view. Thus we have the curious
circumstance of gently formed singlet positronium annihalating to two
511 keV photons, implying the furiously orbiting electrons prior to
annihalation have zero summed kinetic energy.
[quote:38245d8823]I was going to post this to sci.physics.particle but that site looked
a little . . . scary . . . I guess.
Thanks much,
EdV
[/quote:38245d8823]
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2 |
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| FrediFizzx... |
| Posted: Fri Oct 16, 2009 8:37 pm |
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"EdV" <edvogel56 at (no spam) gmail.com> wrote in message
news:9277ba1d-5088-42c6-9484-5ef92effa3c5 at (no spam) y21g2000yqn.googlegroups.com...
[quote:ae1e061b42]I remember in high school physics reading that when an electron and an
anti-electron meet they yield two gamma particles.
My question:
What happens to the kinetic energy of the two particles? Does it show
up in the wavelength of the two gamma particles? Or is the kinetic
energy represented in a different particle?
[/quote:ae1e061b42]
Well, you already have some answers for the kinetic energy; more
profound is that the rest mass energy of the two particles is converted
to energy for the newly created gamma photons also. There are no
different particles involved; it is completely explained with the
particles you mention.
[quote:ae1e061b42]I was going to post this to sci.physics.particle but that site looked
a little . . . scary . . . I guess.
[/quote:ae1e061b42]
Yes, "scary" is probably putting it lightly.  The un-moderated
groups are quite over-run with spam and other nonsense.
Best,
Fred Diether
moderator sci.physics.foundations |
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| Bob_S... |
| Posted: Fri Oct 16, 2009 8:38 pm |
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In the rest-frame of the positron and electron, two back-to-back 511 KeV
gammas are emitted isotropically. If the positron-electron pair rest
frame is moving in the Lab, the Lorentz transformation adds the kinetic
energy of the pair to the two gammas.
Bob_S
--
Bob_S |
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| Tom Roberts... |
| Posted: Fri Oct 16, 2009 8:38 pm |
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Uncle Al wrote:
[quote:2afe5e704f]we have the curious
circumstance of gently formed singlet positronium annihalating to two
511 keV photons, implying the furiously orbiting electrons prior to
annihalation have zero summed kinetic energy.
[/quote:2afe5e704f]
But, of course, they aren't "furiously orbiting" -- they are in an S
state, which means their angular momentum is zero. They aren't
"orbiting" at all, in the sense of moving around each other. This is
indeed as "gentle" as such an annihilation gets; it also has the
shortest lifetime of all possible positronium states (~125 ps).
Tom Roberts |
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| Richard D. Saam... |
| Posted: Fri Oct 16, 2009 9:28 pm |
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EdV wrote:
[quote:d27a29d2e7]I remember in high school physics reading that when an electron and an
anti-electron meet they yield two gamma particles.
My question:
What happens to the kinetic energy of the two particles? Does it show
up in the wavelength of the two gamma particles? Or is the kinetic
energy represented in a different particle?
I was going to post this to sci.physics.particle but that site looked
a little . . . scary . . . I guess.
Thanks much,
EdV
your question is answered adequately in other posts,[/quote:d27a29d2e7]
but I will call your attention to another related question
with respect to conditions necessary
to form particles pairs from a vacuum,
a process commonly called Schwinger Pair Production.
http://arXiv.org/abs/physics/0612173
The required photonic energies are considerable
and not yet achieved by existing lasers
although experiments are planned.
Richard D. Saam |
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| FrediFizzx... |
| Posted: Sun Oct 18, 2009 10:57 pm |
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"Richard D. Saam" <rdsaam at (no spam) att.net> wrote in message
news:s92dnZmw2MyQukTXnZ2dnUVZ_t6dnZ2d at (no spam) giganews.com...
[quote]EdV wrote:
I remember in high school physics reading that when an electron and
an
anti-electron meet they yield two gamma particles.
My question:
What happens to the kinetic energy of the two particles? Does it
show
up in the wavelength of the two gamma particles? Or is the kinetic
energy represented in a different particle?
I was going to post this to sci.physics.particle but that site looked
a little . . . scary . . . I guess.
Thanks much,
EdV
your question is answered adequately in other posts,
but I will call your attention to another related question
with respect to conditions necessary
to form particles pairs from a vacuum,
a process commonly called Schwinger Pair Production.
http://arXiv.org/abs/physics/0612173
The required photonic energies are considerable
and not yet achieved by existing lasers
although experiments are planned.
[/quote]
Also,
http://arxiv.org/abs/hep-ph/0304139
"Boiling the Vacuum with an X-Ray Free Electron Laser"
I am wondering if the new LCLS at SLAC is planning to eventually test
the Schwinger Mechanism?
http://lcls.slac.stanford.edu/
I did a quick search and didn't see anything about it.
Best,
Fred Diether
moderator sci.physics.foundations |
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| Richard D. Saam... |
| Posted: Mon Oct 19, 2009 8:13 pm |
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Guest
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FrediFizzx wrote:
[quote]"Richard D. Saam" <rdsaam at (no spam) att.net> wrote in message
news:s92dnZmw2MyQukTXnZ2dnUVZ_t6dnZ2d at (no spam) giganews.com...
EdV wrote:
I remember in high school physics reading that when an electron and an
anti-electron meet they yield two gamma particles.
My question:
What happens to the kinetic energy of the two particles? Does it show
up in the wavelength of the two gamma particles? Or is the kinetic
energy represented in a different particle?
I was going to post this to sci.physics.particle but that site looked
a little . . . scary . . . I guess.
Thanks much,
EdV
your question is answered adequately in other posts,
but I will call your attention to another related question
with respect to conditions necessary
to form particles pairs from a vacuum,
a process commonly called Schwinger Pair Production.
http://arXiv.org/abs/physics/0612173
The required photonic energies are considerable
and not yet achieved by existing lasers
although experiments are planned.
Also,
http://arxiv.org/abs/hep-ph/0304139
"Boiling the Vacuum with an X-Ray Free Electron Laser"
I am wondering if the new LCLS at SLAC is planning to eventually test
the Schwinger Mechanism?
http://lcls.slac.stanford.edu/
I did a quick search and didn't see anything about it.
Best,
Fred Diether
moderator sci.physics.foundations
In addition I am wondering if the National Ignition Facility (NIF)[/quote]
https://lasers.llnl.gov/
has detected the Schwinger Pair Production
It is clearly not the objective of NIF to look for
Schwinger Pair Production from vacuum
in that its 192 lasers are aimed towards
a BB-sized target filled with hydrogen fuel
to implement fusion
but ???
the obvious experiment is to intersect all
or a portion of the 192 laser beams in vacuum (no BB target)
to observed the possibility of Schwinger Pair Production from vacuum.
Energies and intensities appear adequate.
The sensors are in place.
Even a null result would be scientifically interesting.
I have asked the appropriate DOE people three times
with no answer.
The question begs an answer.
Richard D. Saam |
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