# Feynman Diagram: Simga+ -> p + gamma?

1. May 2, 2012

### Dr.Brule

Feynman Diagram: Simga+ --> p + gamma?

Hi,

Can anyone give me some indications as to how to draw the feynman diagram for the following decay?

Ʃ+ → p + $\gamma$

Should I consider the quark composition of the sigma first?

Thanks a lot.

2. May 3, 2012

### Steely Dan

Re: Feynman Diagram: Simga+ --> p + gamma?

Indeed. All of the QED/QCD interactions involve individual quarks and leptons, not composite particles. So you want to consider what happens to each quark in the sigma particle independently (at least, to get a first approximation to the decay).

3. May 4, 2012

### Dr.Brule

Re: Feynman Diagram: Simga+ --> p + gamma?

So I get how the two u quarks would combine with a d quark to form the proton, but would you get this d quark with the s quark that's left?

Is the process s --> u + anti u ---> ONE gamma allowed?

4. May 4, 2012

### fzero

Re: Feynman Diagram: Simga+ --> p + gamma?

No, that process does not conserve electric charge. What weak interaction processes involving quarks did you learn about?