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 P: 86 Hey guys, one quick question about Wick contractions and derivatives: Suppose I want to write down all (non-vacuum) Wick contractions of two fields a, and one field A into a cubic QCD-like interaction term of the form $\partial^\nu A^{\mu, a}(p_1) a_\mu^b(p_2) a_\nu^c(p_3) f^{abc}$ to get the corresponding Feynman rule (where each field carries also a color index). How do I cope with the derivative? Normally I'd do a Fourier transform, but how do I know to which field the momentum belongs to? In other words if I Fourier trafo the derivative will it become a $p_1$, $p_2$, or $p_3$? Cheers, earth2