Sp(2) Invariant BRST formalism, Supersymmetry and Wess-Zumino gauges

Covariant quantization of Fermi-Bose supersymmetric gauge theories is formulated within an enlarged superspace (xµ, θα, ξm) with manifest ξ-supertranslation (=extended BRST) and Sp(2) invariance. In Wess-Zumino gauges, the correct ghost and auxiliary field structure emerges by counting arguments for the (N=1) super-Yang-Mills, conformal and Einstein supergravity cases. The super-Yang-Mills case is analyzed in detail for both supercovariant and Wess-Zumino gauge-fixing, with particular emphasis on the Sp(2) assignments of the ghost superfields.