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 ${\alpha }_s$ has been measured with several methods giving a global average ${\alpha }_s(M_Z)=0.122\pm 0.004$. The flavour independence of ${\alpha }_s$ has been tested obtaining ${\alpha }_s^b/{\alpha }_s^{udsc}=0.997\pm 0.023$. 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.

1 uuencoded PostScript file. Invited talk at Les Rencontres de Physique de la Vallée d'Aoste, La Thuile, March 3-9, 1996