# Pair Annihilation Problems

1. Sep 22, 2004

### CollectiveRocker

Does anyone know how to solve a pair annihilation problem ( positron and electron), for the energy of the resulting particles, in this case photons?

2. Sep 22, 2004

### Gonzolo

Yes, I would believe that many people here can do that, perhaps even myself.

3. Sep 22, 2004

### zefram_c

We certainly do, but we don't do other people's homework here. Try asking your particular problem in the homework help forum, along with some information on how far you got and where you got stuck.

4. Sep 22, 2004

### CollectiveRocker

I attempted to use the relativistic version of kinetic energy: mc^2(gamma - 1), and solved for gamma. I then put that answer into the relatistic equation for momentum, p = gamma * mv; took that answer and put it into E = pc. That is where i got confused, for the answer was incorrect. The thing which throws off the entire problem is that the electron is at rest when the positron hits it. Any advice?

5. Sep 22, 2004

### zefram_c

6. Sep 23, 2004

### marlon

And keep in mind that collision-problems are solved using conservation of energy and momentum

regards
marlon

7. Oct 3, 2004

### CollectiveRocker

I have solved the problem with conservation of energy and momentum. Thank you fellas.