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photon anti-photon pairs
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Chalky
Feb 12, 2012, 8:18:02 PM2/12/12
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Can photon anti-photon pairs be detected in eg cloud chambers?
If so, does that cause the collapse of the wavefunction, and the
destruction of the photon and anti-photon ?
If so, does that cause the collapse of the wavefunction, and the
destruction of the photon and anti-photon ?
Tom Roberts
Feb 13, 2012, 12:10:01 PM2/13/12
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On 2/12/12 2/12/12 7:18 PM, Chalky wrote:
> Can photon anti-photon pairs be detected in eg cloud chambers?
By "photon" I assume you mean the particle bearing that name in QED and the
> Can photon anti-photon pairs be detected in eg cloud chambers?
standard model; then the photon is its own antiparticle. If this assumption is
wrong, you need to explain what you mean.
Photons are not detectable by cloud chambers, because they are uncharged and a
cloud chamber can only detect the transit of charged particles. This is true of
every tracking detector we have -- the electromagnetic interactions of the
particle with the detector are detected as it ionizes some atoms of the detector
in a way that the detector can detect them (in a cloud chamber, the ionization
nucleates condensation of the supersaturated gas, which can then be photographed).
Photons are completely undetectable by any means until they interact, and they
can do that only once, so they cannot be tracked at all.
> If so, does that cause the collapse of the wavefunction, and the
> destruction of the photon and anti-photon ?
annihilation", because a) photons are their own antiparticles, b) there is no
vertex in the theory that does that, and c) one cannot, in practice, make two of
them interact with each other. Electrons and protons annihilate with their
antiparticles, because they are oppositely charged and therefore attract each
other over large distances and can capture into a two-particle state that has
significant overlap between the two particles so they annihilate.
Also, a "wavefunction" that might "collapse" is only useful in non-relativistic
quantum mechanics, not in (relativistic) quantum field theory, which is needed
to describe photons and their interactions.
Tom Roberts
Lester Welch
Feb 14, 2012, 4:53:19 AM2/14/12
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Chalky
Feb 16, 2012, 3:48:54 AM2/16/12
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On Feb 13, 5:10=A0pm, Tom Roberts <tjroberts...@sbcglobal.net> wrote:
> If this assumption is
> wrong, you need to explain what you mean.
>
> Photons are not detectable by cloud chambers, because they are uncharged and a
> cloud chamber can only detect the transit of charged particles. This is true of
> every tracking detector we have -- the electromagnetic interactions of the
> particle with the detector are detected as it ionizes some atoms of the detector
> in a way that the detector can detect them (in a cloud chamber, the ionization
> nucleates condensation of the supersaturated gas, which can then be photographed).
Thanks for that clarification
annihilation. I had in mind their mutual creation in high energy
physics, and was checking whether they could be detected without
resultant destruction
> Also, a "wavefunction" that might "collapse" is only useful in non-relativistic
> quantum mechanics, not in (relativistic) quantum field theory, which is needed
> to describe photons and their interactions.
???
> On 2/12/12 2/12/12 =A0 7:18 PM, Chalky wrote:
>
> > Can photon anti-photon pairs be detected in eg cloud chambers?
>
> By "photon" I assume you mean the particle bearing that name in QED and the
> standard model; then the photon is its own antiparticle.
Yes, I understand that
>
> > Can photon anti-photon pairs be detected in eg cloud chambers?
>
> By "photon" I assume you mean the particle bearing that name in QED and the
> standard model; then the photon is its own antiparticle.
> If this assumption is
> wrong, you need to explain what you mean.
>
> Photons are not detectable by cloud chambers, because they are uncharged and a
> cloud chamber can only detect the transit of charged particles. This is true of
> every tracking detector we have -- the electromagnetic interactions of the
> particle with the detector are detected as it ionizes some atoms of the detector
> in a way that the detector can detect them (in a cloud chamber, the ionization
> nucleates condensation of the supersaturated gas, which can then be photographed).
>
> Photons are completely undetectable by any means until they interact, and they
> can do that only once, so they cannot be tracked at all.
That is what I thought, but was just checking to make sure :-)
> Photons are completely undetectable by any means until they interact, and they
> can do that only once, so they cannot be tracked at all.
>
> > If so, does that cause the collapse of the wavefunction, and the
> > destruction of the photon and anti-photon ?
>
> I think you are confused. There is no possibility of "photon + anti-photon
> annihilation", because a) photons are their own antiparticles, b) there is no
> vertex in the theory that does that, and c) one cannot, in practice, make two of
> them interact with each other.
Actually, I never meant to ask about mutual photon + anti-photon
> > If so, does that cause the collapse of the wavefunction, and the
> > destruction of the photon and anti-photon ?
>
> I think you are confused. There is no possibility of "photon + anti-photon
> annihilation", because a) photons are their own antiparticles, b) there is no
> vertex in the theory that does that, and c) one cannot, in practice, make two of
> them interact with each other.
annihilation. I had in mind their mutual creation in high energy
physics, and was checking whether they could be detected without
resultant destruction
> Also, a "wavefunction" that might "collapse" is only useful in non-relativistic
> quantum mechanics, not in (relativistic) quantum field theory, which is needed
> to describe photons and their interactions.
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