Electroweak Precision Tests with GigaZ
  By running the prospective high-energy e^+e^- collider TESLA in the GigaZ mode on the Z resonance, experiments can be performed on the basis of more than 10^9 Z events. This will allow the measurement of the effective electroweak mixing angle to an accuracy of \delta sin^2(theta_W,eff) \approx \pm 10^-5. The W boson mass is likewise expected to be measurable with an error of \delta M_W \approx \pm 6 MeV near the W^+W^ threshold. We review the electroweak precision tests that can be performed with these high precision measurements within the Standard Model (SM) and its minimal Supersymmetric extension (MSSM). The complementarity of direct measurements at a prospective linear e^+e^- collider and indirect constraints following from measurements performed at GigaZ is emphasized. 
S. Heinemeyer and G. Weiglein