Previously published and as yet unpublished QCD results obtained with the ALEPH detector at LEP1 are presented. The unprecedented statistics allows detailed studies of both perturbative and non-perturbative aspects of strong interactions to be carried out using hadronic Z and tau decays. The studies presented include precise determinations of the strong coupling constant, tests of its avour independence, tests of the SU(3) gauge structure of QCD, study of coherence eects, and measurements of single-particle inclusive distributions and two-particle correlations for many identied baryons and mesons.

A search for neutral Higgs bosons has been performed using the full sample of Z 0 decays collected by the OPAL detector at LEP up to 1995. The data were taken at centre-of-mass energies between 88 GeV and 95 GeV and correspond to an integrated luminosity of approximately 160 pb 1. The present search addresses the processes Z 0 !H 0 Z and h 0 Z , where H 0 is the Higgs boson predicted by the Standard Model and h 0 the lightest neutral scalar Higgs boson predicted in the framework of the Minimal Supersymmetric Standard Model. For the virtual Z 0 boson, Z , the following decay c hannels are considered: Z ! , e + e and +. One candidate event

The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization.2

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An event sample enriched in semileptonic decays of b hadrons is selected using an inclusive lepton selection from approximately 3.0 million hadronic Z 0 decays collected with the OPAL detector. This sample is used to investigate B meson oscillations by reconstructing a proper decay time for the parent of each lepton, using a jet charge method to estimate the production flavour of this parent, and using the lepton charge to tag the decay flavour. We measure the mass difference between the two B 0 d mass eigenstatesFor the B 0 s system, we find ∆m s > 3.1 ps −1 at the 95% confidence level. This limit varies only a little if alternative limit setting approaches are adopted. Regions at higher ∆m s values are also excluded with some methods for setting the limit.By studying the charge symmetry of the B 0 d mixing structure, we are able to constrain possible CP and CPT violating effects. We measure the CP violation parameter Re ǫ B = −0.006 ± 0.010 ± 0.006 and the indirect CPT violating parameter Im δ B = −0.020 ± 0.016 ± 0.006 . If we invoke CPT symmetry, then we obtainRe ǫ B = 0.002 ± 0.007 ± 0.003 .