Name: Lingxiao Xu (email_not_shown)
Date: 05/05/15-04:54:52 PM Z

2 Aliaksandr:

In the amplitude, the color factor is just Tr[T^a.T^b] which equals to \delta^{ab}/2 exactly. So that in the amplitude squared after we sum over color indexes a and b, we have \sum_{a,b} (\delta^{ab}/2) (\delta^{ab}/2)=2, so I just multiply 2 when the amplitude get squared.

Cheers!

Lingxiao Xu

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