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

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Theνe − e − elastic scattering cross-section was measured with a CsI(Tl) scintillating crystal array having a total mass of 187 kg. The detector was exposed to an average reactorνe flux of 6.4 × 10 12 cm −2 s −1 at the Kuo-Sheng Nuclear Power Station. The experimental design, conceptual merits, detector hardware, data analysis and background understanding of the experiment are presented. Using 29882/7369 kg-days of Reactor ON/OFF data, the Standard Model (SM) electroweak interaction was probed at the squared 4-momentum transfer range of Q 2 ∼ 3 × 10 −6 GeV 2 . The ratio of experimental to SM cross-sections of ξ = [1.08 ± 0.21(stat) ± 0.16(sys)] was measured. Constraints on the electroweak parameters (gV , gA) were placed, corresponding to a weak mixing angle measurement of sin 2 θW = 0.251 ± 0.031(stat ) ± 0.024(sys ). Destructive interference in the SMνe−e process was verified. Bounds on anomalous neutrino electromagnetic properties were placed: neutrino magnetic moment at µν e < 2.2 × 10 −10 µB and the neutrino charge radius at −2.1 × 10 −32 cm 2 < r 2 νe < 3.3 × 10 −32 cm 2 , both at 90% confidence level.

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 .

A search of neutrino magnetic moments was carried out at the Kuo-Sheng Nuclear Power Station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of 1 kg −1 keV −1 day −1 near threshold were achieved. Details of the reactor neutrino source, experimental hardware, background understanding and analysis methods are presented. Based on 570.7 and 127.8 days of Reactor ON and OFF data, respectively, at an average Reactor ON electron anti-neutrino flux of 6.4 × 10 12 cm −2 s −1 , the limit on the neutrino magnetic moments of µν e < 7.4 × 10 −11 µB at 90% confidence level was derived. Indirect bounds on theνe radiative decay lifetimes were inferred.

A search of neutrino magnetic moment was carried out at the Kuo-Sheng Nuclear Power Station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of 1 kg(-1) keV(-1) day(-1) at 12-60 keV were achieved. Based on 4712 and 1250 h of reactor ON and OFF data, respectively, the limit on the neutrino magnetic moment of mu(nu;(e))<1.3x10(-10)mu(B) at 90% confidence level was derived. An indirect bound of the nu;(e) radiative lifetime of m(3)(nu)tau(nu)>2.8x10(18) eV(3) s can be inferred.

The production rates of D * ± mesons in charm and bottom events at centre-of-mass energies of about 91 GeV and the partial width of primary cc pairs in hadronic Z 0 decays have been measured at LEP using almost 4.4 million hadronic Z 0 decays collected with the OPAL detector between 1990 and 1995. Using a combination of several charm quark tagging methods based on fully and partially reconstructed D * ± mesons, and a bottom tag based on identified muons and electrons, the hadronisation fractions of charm and bottom quarks into D * ± mesons have been found to be f (b → D * + X) = 0.173 ± 0.016 ± 0.012 and f (c → D * + X) = 0.222 ± 0.014 ± 0.014 .The fraction of cc events in hadronic Z 0 decays, Γ cc /Γ had = Γ(Z 0 → cc)/Γ(Z 0 → hadrons), is determined to be Γ cc /Γ had = 0.180 ± 0.011 ± 0.012 ± 0.006 .In all cases the first error is statistical, and the second one systematic. The last error quoted for Γ cc /Γ had is due to external branching ratios.

The longitudinal polarization, the transverse polarization, and the forward-backward asymmetry of Λ baryons, have been measured using a sample of 4.34 million hadronic Z 0 decays collected with the OPAL detector at LEP between 1990 and 1995. These results are important as an aid to the understanding of hadronization mechanisms. Significant longitudinal polarization has been observed at intermediate and high momentum. For x E (≡ 2E Λ / √ s) > 0.3, the longitudinal polarization has been measured to be −32.9 ± 5.5 (stat) ± 5.2 (syst)%. We have observed no transverse polarization. A significant forward-backward asymmetry has been measured and can be described by a JETSET model.