QCD Studies at LEP I

Abstract

The high hadronic event statistics collected at the Z energy (LEP I) allowed a good understanding of the QCD dynamics. The coupling constant $α_s$ has been measured with several methods giving a global average $α_s(M_Z) = 0.122 \pm 0.004$. The flavour independence of $α_s$ has been tested obtaining $α_s^b/α_s^{udsc} = 0.997 \pm 0.023$. Quark-gluon jet differencies has been observed among which $<n>_{gluon}/<n>_{quark} = 1.234 \pm 0.027$. A big role has been plaied by the silicon vertex detectors.