Can e+e- collisions produce e+e- pairs through two-photon processes?

  • Context: Graduate 
  • Thread starter Thread starter Monitor16807
  • Start date Start date
  • Tags Tags
    Annihilation Antimatter
Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
Sign up Log in
6 replies · 3K views
Monitor16807
Messages
11
Reaction score
1
Hi, I don't think I understand why antimatter annihilates when it touches matter, should I picture has it as if it was a wave that canceled an other one?

Or is it something else entirely?

Thanks.
 
Physics news on Phys.org
The best answer is probably because it can!
For two particles to be able to annihilate each other you have to be able to balance all the conserved quantities (charge, spin, momentum ) this is only possible if one of the particles is the anti-particle of the other.
 
Well while I'm here I might ask.

I read that 1 electron and 1 positron annihilate to make a gamma ray of 512 Mev, can you take a gamma rays of 512 Mev and make 1 electron and 1 positron?
 
You need to make a pair of gamma rays to balance the momentum - but yes you can collide two gamma rays and create an electron-positron pair.
ps. An electron is 511 KeV ( or 0.511MeV )
 
mgb_phys said:
You need to make a pair of gamma rays to balance the momentum - but yes you can collide two gamma rays and create an electron-positron pair.

Actually, gamma-gamma collision is not very likely yet (very small cross-section), and so far, we haven't produced any e-p pair that way.

Zz.
 
ZapperZ said:
Actually, gamma-gamma collision is not very likely yet (very small cross-section), and so far, we haven't produced any e-p pair that way.

I'm not so sure that's true. There are what are called two-photon processes in e+e- collisions. What happens is that the electron and positron beams get near each other, and each beam feels an acceleration from the other, and radiates a photon: these photons can then interact and produce anything that couples to the photon: including an e+e- pairs. In a sense, you use the electrons to "carry the photons around" pre-collision.

So the process would be [tex]e^+ + e^- \rightarrow e^+ + e^- + \gamma + \gamma \rightarrow e^+ + e^- + e^+ + e^-[/tex].