Determining the $\beta$-function of the strong interaction and closing the light gluino window

We discuss the perturbative running of alpha_s in a model independent way. Our analysis contains the data on the hadronic tau decay and all the total hadronic cross sections in e+e- annihilation between 5 GeV and M_Z. We determine the color coefficients and the perturbative beta-function of the strong interaction. The perturbative approach shows a nice convergence of the confidence level (CL) regions. The results are in agreement with QCD and rule out the QCD+light gluino scenario on the 90% CL. We combine our method with that of the multi-jet analysis at LEP. The combined result rules out light gluinos on the 99% CL.