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Cross-sections and angular distributions for hadronic and lepton pair final states in e+e− collisions at a centre-of-mass energy near 189 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of the Standard Model. The results are used to measure the energy dependence of the electromagnetic coupling constant αem, and(More)
The measurement of small–angle Bhabha scattering is used to determine the luminosity at the OPAL interaction point for the LEP I data recorded between 1993 and 1995. The measurement is based on the OPAL Silicon-Tungsten Luminometer which is composed of two calorimeters encircling the LEP beam pipe, on opposite sides of the interaction point. The luminometer(More)
A search is described to detect charged Higgs bosons via the process ee → HH, using data collected by the OPAL detector at center-of-mass energies of 130−172 GeV with a total integrated luminosity of 25 pb. The decay channels are assumed to be H → qq and H → τντ . No evidence for charged Higgs boson production is observed. The lower limit for its mass is(More)
Two natural and efficient stopping criteria are derived for conjugate gradient (CG) methods, based on iteration parameters. The derivation makes use of the inner product matrix B defining the CG method. In particular, the relationship between the eigenvalues and B-norm of a matrix is investigated, and it is shown that the ratio of largest to smallest(More)
Recently SCRAM (Software Configuration And Management) has been adopted by the applications area of the LHC computing grid project as baseline configuration management and build support infrastructure tool. SCRAM is a software engineering tool, that supports the configuration management and management processes for software development. It resolves the(More)
Searches for unstable neutral and charged heavy leptons, N and L±, and for excited states of neutral and charged leptons, ν∗, e∗, μ∗, and τ∗, have been performed in e+e− collisions using data collected by the OPAL detector at LEP. The data analysed correspond to an integrated luminosity of about 58 pb−1 at a centre-of-mass energy of 183 GeV, and about 10(More)
We present an observation at LEP of the production of χc2 mesons in the collisions of two quasireal photons using the OPAL detector. The χc2 mesons are reconstructed in the decay channel χc2 → J/ψ γ → l l γ (with l = e, μ) using all data taken at ee centre-of-mass energies of 91 and 183 GeV, corresponding to integrated luminosities of 167 and 55 pb(More)
This dissertation focuses on e ciently forming reduced-order models for large, linear dynamic systems. Projections onto unions of Krylov subspaces lead to a class of reducedorder models known as rational interpolants. The cornerstone of this dissertation is a collection of theory relating Krylov projection to rational interpolation. Based on this(More)
Photonic events with large missing energy have been observed in ee collisions at centreof-mass energies of 130, 136 and 183 GeV collected in 1997 using the OPAL detector at LEP. Results are presented for event topologies with a single photon and missing transverse energy or with an acoplanar photon pair. Cross-section measurements are performed within the(More)