One-loop effective action in the $\mathcal N=2$ supersymmetric massive Yang–Mills field theory

We consider the $\mathcal N=2$ supersymmetric massive Yang–Mills field theory formulated in the $\mathcal N=2$ harmonic superspace. We present various gauge-invariant forms of writing the mass term in the action (in particular, using the Stueckelberg superfield), which result in dual formulations of the theory. We develop a gauge-invariant and explicitly supersymmetric scheme of the loop expansion of the superfield effective action beyond the mass shell. In the framework of this scheme, we calculate gauge-invariant and explicitly $\mathcal N=2$ supersymmetric one-loop counterterms including new counterterms depending on the Stueckelberg superfield. We analyze the component structure of one of these counterterms.