Photon decay into positron and electron

In summary: Your Name]In summary, a 3.141 MeV photon cannot spontaneously decay into an electron and positron due to energy conservation. The total energy of the resulting particles would be less than the initial energy of the photon. This decay is possible with the presence of a third particle, known as pair production. The momenta of the photon and electron-positron pair cannot be directly compared, and the momenta of the electron and positron cannot be assumed to be equal.
  • #1
buttermellow7
10
0

Homework Statement


Why can't a 3.141 MeV photon decay spontaneously into an electron and positron, each with rest mass energy .511 MeV?

Homework Equations


Conservation of Momentum and Energy
[tex] E=\sqrt{m^2c^4+p^2c^2} [/tex]
[tex] E_\gamma=pc [/tex]

The Attempt at a Solution


[tex] 3.141=\sqrt{(.511)^2+p^2c^2} [/tex]
[tex] \pm\sqrt{9.866-.261}/c=p [/tex]
[tex] p_e=\pm \frac{3.099}{2} eV/c [/tex]
[tex] p_\gamma=3.141 eV/c [/tex]
[tex] 3.141\neq 3.099 \neq 0 [/tex]

Is this correct? Am I allowed to assume that the momenta of the positron and electron are equal? My feeling in a qualitative perspective is that you could find a frame of reference in which the net velocity of the electron-positron pair is zero, but the velocity of the photon is never zero in any frame. However, my prof told me that gamma ray photons do decay into electrons and positrons? What's the dealio?
 
Physics news on Phys.org
  • #2

Thank you for your question. The reason why a 3.141 MeV photon cannot spontaneously decay into an electron-positron pair is due to energy conservation. In order for this decay to occur, the total energy of the resulting particles (electron + positron) must be equal to the initial energy of the photon (3.141 MeV). However, the rest mass energy of an electron and positron is only 0.511 MeV each, for a total of 1.022 MeV. This means that there is not enough energy available for this decay to occur.

As for the calculation you have attempted, it is not entirely correct. The momentum of the photon and the momentum of the electron-positron pair cannot be directly compared, as they are different types of particles with different properties. The momenta of the electron and positron cannot be assumed to be equal, as they have opposite charges and would therefore have opposite momenta in a magnetic field.

Your professor is correct in saying that gamma ray photons can decay into electron-positron pairs, but this requires the presence of a third particle, such as an atomic nucleus, to conserve energy and momentum. This process is known as pair production and is a common occurrence in high-energy physics.

I hope this helps to clarify the situation. If you have any further questions, please feel free to ask. Remember, science is all about asking questions and seeking answers. Keep up the good work in your studies!
 

1. What is photon decay into positron and electron?

Photon decay into positron and electron refers to the process in which a photon, or a particle of light, spontaneously transforms into a pair of particles: a positron (the antimatter equivalent of an electron) and an electron. This process is also known as pair production.

2. How does photon decay into positron and electron occur?

In order for photon decay into positron and electron to occur, the photon must have enough energy to create the pair of particles. This energy can be provided by collisions with other particles or by being in the presence of a strong electric or magnetic field.

3. What are the implications of photon decay into positron and electron?

The implications of photon decay into positron and electron are significant in the field of particle physics. This process provides evidence for the existence of antimatter and helps to explain the conservation of energy and momentum in particle interactions.

4. Can photon decay into positron and electron be observed?

Yes, photon decay into positron and electron has been observed in laboratory experiments, as well as in natural phenomena such as gamma ray bursts. This process can be detected by observing the energy and direction of the emitted positron and electron.

5. Is photon decay into positron and electron reversible?

Yes, photon decay into positron and electron is reversible. In fact, the reverse process, in which a positron and electron annihilate each other to produce a photon, is also possible and has been observed in experiments. This process is known as pair annihilation.

Similar threads

  • High Energy, Nuclear, Particle Physics
Replies
2
Views
529
  • Introductory Physics Homework Help
Replies
1
Views
865
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
15
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
3K
Replies
1
Views
2K
Replies
23
Views
2K
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
5
Views
1K
Back
Top