8,165 research outputs found

    Data Preservation in High Energy Physics - why, how and when?

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    Long-term preservation of data and software of large experiments and detectors in high energy physics is of utmost importance to secure the heritage of (mostly unique) data and to allow advanced physics (re-)analyses at later times. Summarising the work of an international study group, motivation, use cases and technical details are given for an organised effort to secure and enable future use of past, present and future experimental data. As a practical use case and motivation, the revival of JADE data and the corresponding latest results on measuring αs\alpha_s in NNLO QCD are reviewed.Comment: 5 pages, 3 figures; presentation given at the QCD10, Montpellier, France, June 201

    A Comparison of Unbleached Pulps from Cherry Heartwood and Sapwood

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    The purpose of the project was to evaluate pulps made from cherry heartwood and sapwood. The amount of heartwood a tree has is an individual trait of the tree rather than a function of geography or environment. Tree breeders can, through selection, reduce or increase the amount of heartwood if it is economically justifiable. Three cherry logs with 50-50 heartwood to sapwood ratio were barked and chipped at S.D. Warren Company in Muskegon. The chips were separated, heartwood from sapwood, by the color difference. The chips were cooked using 20% active alkali, 6 to 1 liquor ratio, for 1.5 hours at 175◦C using an oil bath digester. The oil bath digester had six cartridges of which three were charged with heartwood and three with sapwood. The average yield for heartwood was 44.8% and the average yield for sapwood was 52.7%. The difference in yield was the most significant difference between heartwood and sapwood. The brightness of the sapwood was about 5% greater than heartwood. The Kappa number of the heartwood was 20.8 compared to 22.0 for sapwood. The mullen of heartwood was greater than the sapwood in the freeness range of 100 to 500 C.S.F. by 12 to 16%. The tensile of heartwood was greater than the sapwood in the freeness range of 150 to 500 C.S.F. by 4 to 8%. The tear of sapwood was greater than heartwood in the freeness range of 100 to 500 C.S.F. by 14 to 18%. You cannot totally eliminate either heartwood or sapwood and the resulting trade-off of advantages of increasing or decreasing the percent of heartwood would likely result in only a couple percent advantages in a few parameters. Therefore, the conclusion of this paper is to leave the ratio of heartwood to sapwood to nature

    Eleven Years of QCD at LEP

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    Studies of hadronic final states of e+ee^+e^- annihilations, observed at the Large Electron Positron Collider LEP at CERN, are reviewed. The topics included cover measurements of αs\alpha_s, hadronic event shapes and hadronisation studies, tests of asymptotic freedom and of the non-Abelian gauge structure of QCD, differences between quark and gluon jets, tests of power corrections and selected results of two-photon scattering processes. The improvements obtained at LEP are demonstrated by comparing to results from the pre-LEP era. This article consists of a reproduction of slides presented at the LEPFest in October 2000, supplemented by a short descriptive text and a list of relevant references.Comment: 10 pages of text plus reproduction of 27 transparencies presented at the LEPFest at CERN, October 2000. To be published in Eur. Phys. Jour (direct) C; a higher resolution version of the viewgraphs can be obtained from: http://www.mppmu.mpg.de/~bethke/LEPQCDtalk-higres.pd

    Experimental Tests of Asymptotic Freedom

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    Quantum Chromodynamics (QCD), the gauge field theory of the Strong Interaction, has specific features, asymptotic freedom and confinement, which determine the behaviour of quarks and gluons in particle reactions at high and at low energy scales. QCD predicts that the strong coupling strength \as decreases with increasing energy or momentum transfer, and vanishes at asymptotically high energies. In this review, the history and the status of experimental tests of asymptotic freedom are summarised. The world summary of measurements of \as is updated, leading to an unambiguous verification of the running of \as and of asymptotic freedom, in excellent agreement with the predictions of QCD. Averaging a set of measurements balanced between different particle processes and the available energy range, results in a new and improved world average of \amz = 0.1189 \pm 0.0010 .Comment: 38 pages, 18 figure

    Jet Physics at LEP and World Summary of αs\alpha_s

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    Recent results on jet physics and tests of QCD from hadronic final states in e+ee^+e^- annihilation at PETRA and at LEP are reviewed, with special emphasis on hadronic event shapes, charged particle production rates, properties of quark and gluon jets and determinations of αs\alpha_s. The data in the entire energy range from PETRA to LEP-2 are in broad agreement with the QCD predictions. The world summary of measurements of αs\alpha_s is updated and a detailed discussion of various methods to determine the overall error of αs(MZ)\alpha_s (M_Z) is presented. The new world average is αs(MZ)=0.119±0.004\alpha_s (M_Z) = 0.119 \pm 0.004. The size of the error depends on the treatment of correlated uncertainties.Comment: Talk presented at the IVthIV^{th} Int. Symp. on Radiative Corrections, Barcelona, Sept. 8-12, 1998. 18 pages, 13 eps-figures; uses sprocl.sty and psfig.st

    QCD Tests at e+ee^+e^- Colliders

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    A short review of the history and a 'slide-show' of QCD tests in e+ee^+e^- annihilation is given. The world summary of measurements of αs\alpha_s is updated.Comment: Revised version: some references added and corrected; world summary of αs\alpha_s extended by result from polarized structure functions. 9 pages, 15 EPS figures; contribution to the CQD Euroconference 97 (Montpellier 1997

    αs\alpha_s at Zinnowitz 2004

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    A review of measurements of αs\alpha_s is given, representing the status of April 2004. The results prove the energy dependence of αs\alpha_s and are in excellent agreement with the expectations of Quantum Chromodynamics, QCD. Evolving all results to the rest energy of the Z0Z^0 boson, the world average of αs(MZ)\alpha_s(M_Z) is determined from measurements which are based on QCD calculations in complete NNLO perturbation theory, giving αs(MZ)=0.1182±0.0027.\alpha_s(M_Z) = 0.1182 \pm 0.0027 .Comment: 8 pages, 4 figures, talk presented at the workshop Loops and Legs in Quantum Field Theory, April 2004, Zinnowitz (Germany

    Politics and forgiveness

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