Faddeev-Popov antighost field ($b^a={\bar{c}}^a,\mathrm{gh}(b)=-1$)

The Grassmann-odd partner of the Faddeev-Popov ghost field in the gauge-fixing determinant representation. In an auxiliary-field BRST symmetry description it obeys $sb=h$, where $h$ is the Nakanishi-Lautrup field. Its ordinary spacetime derivative remains odd, which matters when moving an anticommuting BRST parameter past it.