Final state QCD studies at LEP: Part I

This is the first of two summaries presented in this conference, of results obtained by the DELPHI and OPAL Collaborations in studies of QCD in the final state, in two-photon and electron-positron collisions at LEP. This talk presents measurements of hadronic cross-sections in two-photon collisions from DELPHI, and thorough studies of QCD in events with 3 jets from DELPHI and from OPAL Collaborations at CERN. DELPHI has studied the charge of leading systems in quark and gluon jets, as well as the contribution of quark and gluon jets to the average event charged multiplicity as a function of the jet energy, and from it measured the ratio 2.261 0.014( .) 0.036( .) 0.066( .) CA F C = ± stat ± exp ± theo . OPAL submitted a report of scaling violations in the quark and gluon fragmentation functions, of which a resume is here included, and measured the average charged particle multiplicity in inclusive hadronic Z0 decays at several centre of mass energies and in flavour selected Z0 decays, obtaining for the inclusive case at 0 Z s = M the value ( 0 ) 20.93 0.01( ch Z n M = ± stat.) ± 0.23(syst.) . All results are preliminary.