Two-loop formfactors in theories with mass gap and Z-boson production

The non-factorizable two-loop corrections to the formfactor both for a U(1)×U(1)U(1)×U(1) and a SU(2)×U(1)SU(2)×U(1) gauge theory with massive and massless gauge bosons respectively are evaluated at arbitrary momentum transfer q2q2. The asymptotic behaviour for q2→∞q2→∞ is compared to a recent calculation of Sudakov logarithms. The result is an important ingredient for the calculation of radiative corrections to Z-boson production at hadron and lepton colliders.