Hi guys! A serious doubt just passed through my mind. It is probably a silly question. In writing the Feynman rules for QCD, we know that the quark-gluon vertex is given by:(adsbygoogle = window.adsbygoogle || []).push({});

$$-ig\gamma_\mu T^a_{ij}$$

where T is the SU(3) generator and i and j are the colors of the incoming and outgoing quarks. My question is: does the quark spinors also brigs indices? If for example I would like to write down the matrix element for a quark interacting with a certain color field [itex]A_\mu(q)[/itex], do I have to write:

$$\bar{u}^i(k)(-ig)T^a_{ij}\gamma^\mu A_\mu^a(q) u^j(k')$$

??

Thank you very much

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# Question on QCD Feynman rules

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