Exact Adler Function in Supersymmetric QCD
  The Adler function D is found {\em exactly} in supersymmetric QCD. Our exact formula relates D(Q^2) to the anomalous dimension of the matter superfields \gamma (\alpha_s(Q^2)). En rout we prove another theorem: the absence of the so-called singlet contribution to D. While such singlet contributions are present in individual supergraphs, they cancel in the sum. 
M. Shifman, K. Stepanyantz
hep-th hep-ph