QuarkGluonVertex[mu, a] gives the Feynman rule for the
quark-gluon vertex.
QGV can be used as an abbreviation of
QuarkGluonVertex.
The dimension and the name of the coupling constant are determined by
the options Dimension and
CouplingConstant.
QuarkGluonVertex[\[Mu], a, Explicit -> True]i g_s T^a.\gamma ^{\mu }
QGV[\[Mu], a]Q_a^{\mu }
Explicit[%]i g_s T^a.\gamma ^{\mu }