# Vector QED Feynman rule

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1. Oct 16, 2015

### Maurice7510

So this isn't a homework problem really, but based on the posting rules for the HEP section this seems to fit better here. My issue is that I'm trying to use a Feynman diagram to represent a Bremsstrahlung process in which a vector particle is produced: $$Z + e^- \rightarrow Z + e^- + v.$$ If I make the lowest order Feynman diagrams of the situation, you get the two in the PDF I attached on here. The problems I have are twofold -- the first is: can I ignore the proton here are just have an incoming photon, thus reducing these diagrams to looking just like the two for Compton scattering (except with outgoing v instead of a photon)? If I can't, how do I find the amplitude from a diagram that looks like this? The second problem is this: regardless of whether or not I can draw this without the proton, what's the vertex factor for $$e^- \rightarrow \e^- + v$$ and what is the external line factor associated ith a vector particle? I've looked all around and can't seem to find the information I need, so any help would be great. Thanks!

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2. Oct 22, 2015