Hi, Vladyslav. Thanks for the fix.
I'm thinking that in a more general setup only the SumOver[...,
External] could be dropped from the conjugate amplitude; all of
the internal ones should be taken into account, in a case of
quark loops in both the left and the right amplitudes.
I'm not sure if there can be IndexDeltas with Generation indices
involved in an internal loop though; if so, then those need to
be summed over *before* the multiplication by the conjugate
amplitude, because FCRenameDummyIndices will not rename them.
I agree that qgraf/FORM/color.h combination is more flexible, of
course. On the other hand it is more bug prone too, so it makes
sense to double-check it with FeynArts+FeynCalc.
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