Photon as composite of electron and positron

Click For Summary

Discussion Overview

The discussion revolves around the nature of photons, specifically whether they can be considered as composite particles made up of an electron and a positron. The conversation touches on concepts from quantum mechanics and particle physics, including pair production and the stability of bound states.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants propose that since a photon can annihilate into an electron and a positron, it might be viewed as a composite of these particles with a total spin of 1.
  • Others argue that while pair production can yield various particles, this does not necessarily support the idea of photons being composite, as they are typically regarded as elementary particles.
  • A participant mentions positronium, a known bound state of an electron and a positron, which decays into photons, suggesting that this indicates photons should be considered elementary unless a more fundamental theory is developed.
  • Concerns are raised about the stability of bound states formed by electrons and positrons, with references to quantum electrodynamics and the nature of their interactions.

Areas of Agreement / Disagreement

Participants express differing views on whether photons can be considered composite particles. Some support the composite view based on annihilation processes, while others maintain that photons are elementary, citing the instability of bound states like positronium.

Contextual Notes

The discussion highlights the complexity of particle interactions and the conditions under which particles can be considered bound states. There are unresolved aspects regarding the definitions of elementary versus composite particles and the implications of quantum electrodynamics.

K S Mallesh
Messages
4
Reaction score
0
A photon annihilates into an electron and a positron (both having spin 1/2). The reverse process is also a reality. Can the photon therefore be viewed as a composite of an electron and a positron having a total spin 1?
 
Physics news on Phys.org
K S Mallesh said:
A photon annihilates into an electron and a positron (both having spin 1/2). The reverse process is also a reality. Can the photon therefore be viewed as a composite of an electron and a positron having a total spin 1?

I once thought this until I discovered that pair production by the photon can also yield other particles.

http://arxiv.org/abs/astro-ph/0111460
V. A. Kudryavtsev
(Submitted on 23 Nov 2001)

Abstract: Production of muon pairs by high-energy photons in electromagnetic and hadronic showers in atmosphere has been calculated.

But I wouldn't be discouraged by what I say. A day doesn't go by that someone here at the forum doesn't ask a question about photon's. I have the feeling that no one is even close to understanding light.
 
A bound state of electron and positron is well-known in nature and it is not stable as it will decay in two photons in 125 picoseconds for the singlet case. This is called positronium. So, photons should be regarded as truly elementary particles unless a more fundamental theory is found with other building blocks.

Anyway you can see this by yourself as electrons and positrons can have only weak and electromagnetic interactions and while the former cannot form bound states due to their extreme weakness, the latter forms bound states but with bound energy of the order of eV making the bonding not that strong. Besides, due to quantum electrodynamics, this bound is not even stable. You should note here a difference with respect to atoms.

Jon
 
Lester said:
A bound state of electron and positron is well-known in nature and it is not stable as it will decay in two photons in 125 picoseconds for the singlet case. This is called positronium. So, photons should be regarded as truly elementary particles unless a more fundamental theory is found with other building blocks.

Anyway you can see this by yourself as electrons and positrons can have only weak and electromagnetic interactions and while the former cannot form bound states due to their extreme weakness, the latter forms bound states but with bound energy of the order of eV making the bonding not that strong. Besides, due to quantum electrodynamics, this bound is not even stable. You should note here a difference with respect to atoms.

Jon

Dear Sir,
Thanks for your reply which contains reasonable aspects that do not favour such composite nature for photons
 

Similar threads

Undergrad Infinite energy from an electric field?
  • · Replies 12 ·
Replies
12
Views
2K
High School 1-photon emission possible from electron-positron annihilation?
  • · Replies 23 ·
Replies
23
Views
4K
Graduate QFT Superposition of Final States
  • · Replies 3 ·
Replies
3
Views
1K
Undergrad Is a Photon Considered a Real Object?
  • · Replies 2 ·
Replies
2
Views
1K
High School Does a photon contain a pair of spinning charges?
  • · Replies 9 ·
Replies
9
Views
2K
Graduate Conservation of angular momentum in positron-electron annihilation
  • · Replies 3 ·
Replies
3
Views
3K
High School Entanglement and pair-production and annihilation
  • · Replies 2 ·
Replies
2
Views
3K
Undergrad The Potential of Back-to-Back Photons: an Experiment
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Question about the Feynmann-Stuckelberg interpretation
  • · Replies 2 ·
Replies
2
Views
1K
High School Does an electron turn into a positron when hit by a photon?
  • · Replies 6 ·
Replies
6
Views
3K