QuarkFieldChi is the name of a fermionic field. This is
just a name with no functional properties. Only typesetting rules are
attached.
QuarkFieldChi\chi
QuantumField[QuarkFieldChiDagger] . GA[\[Mu]] . CovariantD[\[Mu]] . QuantumField[QuarkFieldChi]
ExpandPartialD[%]\chi ^{\dagger }.\bar{\gamma }^{\mu }.D_{\mu }.\chi
\bar{\gamma }^{\mu } \chi ^{\dagger }.\left(\left.(\partial _{\mu }\chi \right)\right)-i T^{\text{c19}} g_s \bar{\gamma }^{\mu } \chi ^{\dagger }.A_{\mu }^{\text{c19}}.\chi