Determining theβFunction of the Strong Interaction Coupling and Closing the Light Gluino Window

We discuss the perturbative running of ${\alpha }_s$ in a model independent way. Our analysis contains data on the hadronic $\tau$ decay and 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 results are in agreement with QCD and rule out the QCD $+$ light gluino scenarios on the 70.8%–93.0% C.L. We combine our method with that of the multijet analysis at LEP. The combined result rules out light gluinos on the 99.76% C.L., provided that nonperturbative effects are not large.