The higher derivative regularization and quantum corrections in ${\cal   N}=2$ supersymmetric theories
  We construct a new version of the higher covariant derivative regularization for a general ${\cal N}=2$ supersymmetric gauge theory formulated in terms of ${\cal N}=1$ superfields. This regularization preserves both supersymmetries of the classical action, namely, the invariance under the manifest ${\cal N}=1$ supersymmetry and under the second hidden on-shell supersymmetry. The regularizing ${\cal N}=2$ supersymmetric higher derivative term is found in the explicit form in terms of ${\cal N}=1$ superfields. Thus, ${\cal N}=2$ supersymmetry is broken only by the gauge fixing procedure. Then we analyze the exact NSVZ $\beta$-function and prove that in the considered model its higher loop structure is determined by the anomalous dimension of the chiral superfield $\Phi$ in the adjoint representation which is the ${\cal N}=2$ superpartner of the gauge superfield $V$. Using the background field method we find that this anomalous dimension is related with the anomalous dimension of the hypermultiplet and vanishes if the effective action is invariant under ${\cal N}=2$ background supersymmetry. As a consequence, in this case the higher loop contributions to $\beta$-function also vanish. The one-loop renormalization structure in the considered regularization is also studied by the explicit calculations of the one-loop renormalization constants. 
I.L.Buchbinder, K.V.Stepanyantz
hep-th