Identical particles and Feynman diagrams

[taishizhiqiu]

In Introduction to QFT (peskin) 4.5, he writes:

The computation for M, of course, will be quite different when identical particles are present.

However, I have finished reading the first part of the book and found no special treatment for identical particles. Can anybody tell me how to compute M if identical particles are present?

 

[WannabeNewton]

There is a combinatorial factor you must divide by when computing the amplitude for a scattering process involving identical particles. It's in the Feynman rules so look in the index for the section on them.

 

[taishizhiqiu]

There is a combinatorial factor you must divide by when computing the amplitude for a scattering process involving identical particles. It's in the Feynman rules so look in the index for the section on them.

But that's not about computing M matrix. So basically there's nothing special for identical particles?

 

[Avodyne]

Different Feynman diagrams contribute if the particles are identical. For example, electron-muon scattering has only one diagram at tree level (t-channel photon exchange), but electron-electron scattering has two (t-channel and u-channel photon exchange).