Hadronic contributions to the running fine structure constant α(mz2) from QCD sum rules

The value of the QED running coupling constant α(mz2) is very important for precision tests of the standard model. A purely theoretical calculation of the hadronic part Δαh(mz2) using QCD and the analytic properties of the vacuum polarisation tensor is presented. We obtain Δαh(mz2) = 0.0267 ± 0.0011.