3,414 research outputs found

    Virtual effects of light gauginos and higgsinos: a precision electroweak analysis of split supersymmetry

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    We compute corrections to precision electroweak observables in supersymmetry in the limit that scalar superpartners are very massive and decoupled. This leaves charginos and neutralinos and a Standard Model-like Higgs boson as the only states with unknown mass substantially affecting the analysis. We give complete formulas for the chargino and neutralino contributions, derive simple analytic results for the pure gaugino and higgsino cases, and study the general case. We find that in all circumstances, the precision electroweak fit improves when the charginos and neutralinos are near the current direct limits. Larger higgsino and gaugino masses worsen the fit as the theory predictions asymptotically approach those of the Standard Model. Since the Standard Model is considered by most to be an adequate fit to the precision electroweak data, an important corollary to our analysis is that all regions of parameter space allowed by direct collider constraints are also allowed by precision electroweak constraints in split supersymmetry.Comment: 22 pages, 5 figures, v2: typos fixed and note adde

    WW Cross-sections and Distributions

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    We present the results obtained by the "WW Cross-sections and Distributions" working group during the CERN Workshop "Physics at LEP2" (1994/1995)Comment: 61 pages, tar'ed gzip'ed uuencoded files, LaTeX, 4 Postscript figures. To appear in "Physics at LEP2", G.Altarelli and F.Zwirner eds., CERN Report 199

    Review of the Properties of the W Boson at LEP, and the Precision Determination of its Mass

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    We review the precision measurement of the mass and couplings of the W Boson at LEP. The total and differential W+W- cross section is used to extract the WWZ and WWgamma couplings. We discuss the techniques used by the four LEP experiments to determine the W mass in different decay channels, and present the details of methods used to evaluate the sources of systematic uncertainty.Comment: 97 page

    Data Mining Activities for Bone Discipline - Current Status

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    The disciplinary goals of the Human Research Program are broadly discussed. There is a critical need to identify gaps in the evidence that would substantiate a skeletal health risk during and after spaceflight missions. As a result, data mining activities will be engaged to gather reviews of medical data and flight analog data and to propose additional measures and specific analyses. Several studies are briefly reviewed which have topics that partially address these gaps in knowledge, including bone strength recovery with recovery of bone mass density, current renal stone formation knowledge, herniated discs, and a review of bed rest studies conducted at Ames Human Research Facility

    Two-Fermion Production in Electron-Positron Collisions

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    This report summarizes the results of the two-fermion working group of the LEP2-MC workshop, held at CERN from 1999 to 2000. Recent developments in the theoretical calculations of the two fermion production process in the electron-positron collision at LEP2 center of the mass energies are reported. The Bhabha process and the production of muon, tau, neutrino and quark pairs is covered. On the basis of comparison of various calculations, theoretical uncertainties are estimated and compared with those needed for the final LEP2 data analysis. The subjects for the further studies are identified.Comment: 2-fermion working group report of the LEP2 Monte Carlo Workshop 1999/2000, 113 pages, 24 figures, 35 table

    GATE : a simulation toolkit for PET and SPECT

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    Monte Carlo simulation is an essential tool in emission tomography that can assist in the design of new medical imaging devices, the optimization of acquisition protocols, and the development or assessment of image reconstruction algorithms and correction techniques. GATE, the Geant4 Application for Tomographic Emission, encapsulates the Geant4 libraries to achieve a modular, versatile, scripted simulation toolkit adapted to the field of nuclear medicine. In particular, GATE allows the description of time-dependent phenomena such as source or detector movement, and source decay kinetics. This feature makes it possible to simulate time curves under realistic acquisition conditions and to test dynamic reconstruction algorithms. A public release of GATE licensed under the GNU Lesser General Public License can be downloaded at the address http://www-lphe.epfl.ch/GATE/

    A Combination of Preliminary Electroweak Measurements and Constraints on the Standard Model, 1996

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    This note presents a combination of published and preliminary electroweak results from the four LEP collaborations and the SLD collaboration which were prepared for the 1996 summer conferences. Averages of the results concerning electroweak physics are presented. They are derived from the measurements of hadronic and leptonic cross sections, the leptonic forward-backward asymmetries, the τ\tau polarisation asymmetries, the \bb and \cc partial widths and forward-backward asymmetries and the \qq charge asymmetry. Almost every measurement including the LEP beam energy calibration has been updated with respect to the summer 1995 conferences. The results are compared to precise electroweak measurements from other experiments. The parameters of the Standard Model are evaluated, first using the combined LEP electroweak measurements, and then using the full set of precise electroweak results

    Measurements of the Cross Section for e+e- -> hadrons at Center-of-Mass Energies from 2 to 5 GeV

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    We report values of R=σ(e+ehadrons)/σ(e+eμ+μ)R = \sigma(e^+e^-\to {hadrons})/\sigma(e^+e^-\to\mu^+\mu^-) for 85 center-of-mass energies between 2 and 5 GeV measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider.Comment: 5 pages, 3 figure

    Measurements of the continuum RudsR_{\rm uds} and RR values in e+ee^+e^- annihilation in the energy region between 3.650 and 3.872 GeV

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    We report measurents of the continuum RudsR_{\rm uds} near the center-of-mass energy of 3.70 GeV, the Ruds(c)+ψ(3770)(s)R_{{\rm uds(c)}+\psi(3770)}(s) and the Rhad(s)R_{\rm had}(s) values in e+ee^+e^- annihilation at 68 energy points in the energy region between 3.650 and 3.872 GeV with the BES-II detector at the BEPC Collodier. We obtain the RudsR_{\rm uds} for the continuum light hadron (containing u, d and s quarks) production near the DDˉD\bar D threshold to be Ruds=2.141±0.025±0.085R_{\rm uds}=2.141 \pm 0.025 \pm 0.085.Comment: 5 pages, 3 figure

    Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma)

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    The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08 ^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical, the second systematic and the third is associated to the ratio of fragmentation fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/- 0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be (3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.Comment: 15 pages, 1 figure, 2 table
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