47,427 research outputs found

    W Mass at LEP and Standard Model Fits

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    The W-mass measurements from LEP and the results of a global fit of the Standard Model parameters to the electroweak data are presented. Comprehensive studies of experimental systematic effects allowed a measurement of the W mass with an accuracy of better than half a permill. Especially the recent improvements in the LEP energy calibration, the modelling of the hadronisation process and the understanding of Bose-Einstein correlations and colour reconnection effects are discussed. The fit of the Standard Model parameters to all electroweak measurements verifies the self-consistency of the theory. The combination of all electroweak data yield information on the mass of the still undiscovered Higgs boson, mHm_H.Comment: Proceedings of the XLIst Recontres de Moriond, La Thuile, March 200

    The scatter of mechanical values of carbon fiber composites and its causes

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    The scatter of experimental data obtained in an investigation of the parameters of structural components was investigated. Strength parameters which are determined by the resin or the adhesion between fiber and resin were included. The statistical characteristics of the mechanical parameters of carbon fiber composites, and the possibilities which exist to reduce this scatter were emphasized. It is found that quality control tests of fiber and resin are important for such a reduction

    Binary hard-sphere fluids near a hard wall

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    By using the Rosenfeld density functional we determine the number density profiles of both components of binary hard-sphere fluids close to a planar hard wall as well as the corresponding excess coverage and surface tension. The comparison with published simulation data demonstrates that the Rosenfeld functional, both its original version and sophistications thereof, is superior to previous approaches and exhibits the same excellent accuracy as known from studies of the corresponding one-component system

    Electroweak Radiative Corrections to Off-Shell W-Pair Production

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    We briefly describe the RacoonWW approach to calculate radiative corrections to e+ e- -> W W -> 4 fermions and present numerical results for the total W-pair production cross section at LEP2.Comment: 3 pages, 2 figures, talk given at the DPF2000 meeting, Columbus, OH, August 9-12, 200

    A Piecewise Linear State Variable Technique for Real Time Propulsion System Simulation

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    The emphasis on increased aircraft and propulsion control system integration and piloted simulation has created a need for higher fidelity real time dynamic propulsion models. A real time propulsion system modeling technique which satisfies this need and which provides the capabilities needed to evaluate propulsion system performance and aircraft system interaction on manned flight simulators was developed and demonstrated using flight simulator facilities at NASA Ames. A piecewise linear state variable technique is used. This technique provides the system accuracy, stability and transient response required for integrated aircraft and propulsion control system studies. The real time dynamic model includes the detail and flexibility required for the evaluation of critical control parameters and propulsion component limits over a limited flight envelope. The model contains approximately 7.0 K bytes of in-line computational code and 14.7 K of block data. It has an 8.9 ms cycle time on a Xerox Sigma 9 computer. A Pegasus-Harrier propulsion system was used as a baseline for developing the mathematical modeling and simulation technique. A hydromechanical and water injection control system was also simulated. The model was programmed for interfacing with a Harrier aircraft simulation at NASA Ames. Descriptions of the real time methodology and model capabilities are presented

    Sympathetic cooling of 4^4He+^+ ions in a radiofrequency trap

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    We have generated Coulomb crystals of ultracold 4^4He+^+ ions in a linear radiofrequency trap, by sympathetic cooling via laser--cooled 9^9Be+^+. Stable crystals containing up to 150 localized He+^+ ions at \sim20 mK were obtained. Ensembles or single ultracold He+^+ ions open up interesting perspectives for performing precision tests of QED and measurements of nuclear radii. The present work also indicates the feasibility of cooling and crystallizing highly charged atomic ions using 9^9Be+^+ as coolant.Comment: 4 pages, 2 figure
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