Pair Production and Annihilation

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Discussion Overview

The discussion revolves around the processes of pair production and annihilation in the context of photon interactions, focusing on the energy dynamics involved in these phenomena. Participants explore the relationship between the energy of the incoming photon and the resulting particles, as well as the characteristics of the photons produced during annihilation.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that the energy of the incoming photon must equal the combined rest mass of the electron and positron produced during pair production.
  • Another participant challenges the claim that the new photons from annihilation will each have half the energy of the original photon, stating that the original photon typically has excess energy that contributes to the kinetic energy of the pair.
  • A question is raised regarding whether the parent photon should be expected to have a smaller wavelength than the two daughter photons produced during annihilation.
  • One participant asserts that since wavelength is inversely proportional to energy, the parent photon must have less than half the wavelength of the daughter photons.
  • A correction is offered regarding the distribution of the extra energy in pair production, indicating it goes into the kinetic energy of the nucleus rather than the pair itself.

Areas of Agreement / Disagreement

Participants express differing views on the energy distribution during pair production and annihilation, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

There are assumptions about the energy levels of photons and the specifics of energy distribution that are not fully detailed, leading to potential ambiguities in the discussion.

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When a photon, with the help of a nucleus experiences pair production to make a positron and an electron, the energy of the photon will equal the rest mass of both the electron and positron together right?

Then when the electron and positron annihilate, the two photons produces will each have energy equal to the rest mass of a positron/electron.

The new photons will have half the energy of the original photon each.



Is this correct?
 
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The new photons will have half the energy of the original photon each.
Not quite true. The incoming photon will in general have more energy than that required to create the pair. The extra energy ends up as kinetic energy of the pair.
 
Should it be expected that the parent photon will have a smaller wavelength than the two daughter photons?
 
Since wavelength is inversely proportional to energy, the parent photon has less than half the wavelength of the daughters.

Small correction, the extra energy of the photon in pair production goes into kinetic energy of the nucleus.
 

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