  The $b$ ghost, or $b$ operator, used for fixing Siegel gauge in the pure
spinor superfield formalism, is a composite operator of negative ghost number,
satisfying $\{q,b\}=\square$, where $q$ is the pure spinor differential (BRST
operator). It is traditionally constructed using non-minimal variables.
However, since all cohomology has minimal representatives, it seems likely that
there should be versions of physically meaningful operators, also with negative
ghost number, using only minimal variables. The purpose of this letter is to
demonstrate that this statement holds by providing a concrete construction in
$D=10$ super-Yang-Mills theory, and to argue that it is a general feature in
the pure spinor superfield formalism.
