7,442 research outputs found

    Resummation and Shower Studies

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    The transverse momentum spectra of the Z and Higgs bosons are studied, as probes of the consequences of multiple parton emissions in hadronic events. Emphasis is put on constraints, present in showers, that go beyond conventional leading log. It is shown that, if such constraints are relaxed, better agreement can be obtained with experimental data and with resummation descriptions.Comment: 6 pages, LaTeX, 3 eps figures, submitted to the proceedings of the Workshop on Physics at TeV Colliders, Les Houches, France, 26 May -- 6 June 200

    A Comparison of Predictions for SM Higgs Boson Production at the LHC

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    This paper describes a comparison of most of the available predictions for the cross section and transverse momentum distribution for a 125 GeV mass Higgs at the LHC, including those from the PYTHIA and HERWIG parton shower Monte Carlos and from four resummation calculations.Comment: 7 pages, submitted to proceedings of the Workshop on Physics at TeV Colliders, Les Houches 200

    Report of the QCD Tools Working Group

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    We report on the activities of the ``QCD Tools for heavy flavors and new physics searches'' working group of the Run II Workshop on QCD and Weak Bosons. The contributions cover the topics of improved parton showering and comparisons of Monte Carlo programs and resummation calculations, recent developments in Pythia, the methodology of measuring backgrounds to new physics searches, variable flavor number schemes for heavy quark electro-production, the underlying event in hard scattering processes, and the Monte Carlo MCFM for NLO processes.Comment: LaTeX, 47 pages, 41 figures, 10 tables, uses run2col.sty, to appear in the Proceedings of the Workshop on "QCD and Weak Boson Physics in Run II", Fermilab, March - November 199

    A Field Range Bound for General Single-Field Inflation

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    We explore the consequences of a detection of primordial tensor fluctuations for general single-field models of inflation. Using the effective theory of inflation, we propose a generalization of the Lyth bound. Our bound applies to all single-field models with two-derivative kinetic terms for the scalar fluctuations and is always stronger than the corresponding bound for slow-roll models. This shows that non-trivial dynamics can't evade the Lyth bound. We also present a weaker, but completely universal bound that holds whenever the Null Energy Condition (NEC) is satisfied at horizon crossing.Comment: 16 page

    Effects of acute fatigue on the volitional and magnetically-evoked electromechanical delay of the knee flexors in males and females

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    Neuromuscular performance capabilities, including those measured by evoked responses, may be adversely affected by fatigue; however, the capability of the neuromuscular system to initiate muscle force rapidly under these circumstances is yet to be established. Sex-differences in the acute responses of neuromuscular performance to exercise stress may be linked to evidence that females are much more vulnerable to ACL injury than males. Optimal functioning of the knee flexors is paramount to the dynamic stabilisation of the knee joint, therefore the aim of this investigation was to examine the effects of acute maximal intensity fatiguing exercise on the voluntary and magnetically-evoked electromechanical delay in the knee flexors of males and females. Knee flexor volitional and magnetically-evoked neuromuscular performance was assessed in seven male and nine females prior to and immediately after: (i) an intervention condition comprising a fatigue trial of 30-seconds maximal static exercise of the knee flexors, (ii) a control condition consisting of no exercise. The results showed that the fatigue intervention was associated with a substantive reduction in volitional peak force (PFV) that was greater in males compared to females (15.0%, 10.2%, respectively, p < 0.01) and impairment to volitional electromechanical delay (EMDV) in females exclusively (19.3%, p < 0.05). Similar improvements in magnetically-evoked electromechanical delay in males and females following fatigue (21%, p < 0.001), however, may suggest a vital facilitatory mechanism to overcome the effects of impaired voluntary capabilities, and a faster neuromuscular response that can be deployed during critical times to protect the joint system

    Generic User Process Interface for Event Generators

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    Generic Fortran common blocks are presented for use by High Energy Physics event generators for the transfer of event configurations from parton level generators to showering and hadronization event generators.Comment: Physics at TeV Colliders II Workshop, Les Houches, France, May 2001 14 pages, 6 figure

    Parton Distributions Working Group

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    The main focus of this working group was to investigate the different issues associated with the development of quantitative tools to estimate parton distribution functions uncertainties. In the conclusion, we introduce a "Manifesto" that describes an optimal method for reporting data.Comment: Report of the Parton Distributions Working Group of the 'QCD and Weak Boson Physics workshop in preparation for Run II at the Fermilab Tevatron'. Co-Conveners: L. de Barbaro, S.A. Keller, S. Kuhlmann, H. Schellman, and W.-K. Tun

    CONSTITUTIONAL LAW-DUE PROCESS-BILL OF ATTAINDER-LOYALTY OATHS FOR CITY EMPLOYEE

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    In 1948, pursuant to an amendment to its charter, Los Angeles passed an ordinance which provided that all city employees must (1) take an oath that they did not espouse, and had not espoused within five years prior to the effective date of the ordinance, the forceful overthrow of the government; that they were not, nor had they been within the same period, affiliated with a group espousing such aims, and that they would not join any such group while in city employ, and (2) execute an affidavit relating whether they had ever belonged to the Communist Party, and if so the dates of their membership. Two appellants took the oath but refused to execute the affidavit; the remaining fifteen appellants refused to comply with either part of the ordinance. All were discharged, and sued for reinstatement and back salaries. The California Court of Appeals denied relief; certiorari was granted by the United States Supreme Court. Held, affirmed, Justices Black and Douglas dissenting, and Justices Frankfurter and Burton dissenting in part. The ordinance was a reasonable regulation of its employees by the city; it did not constitute a bill of attainder, or deny the appellants due process of law. Garner v. Board of Public Works of City of Los Angeles, 341 U.S. 716, 71 S.Ct. 909 (1951)

    Prompt photons at RHIC

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    We calculate the inclusive cross section for prompt photon production in heavy-ion collisions at RHIC energies (s=130\sqrt{s}=130 GeV and s=200\sqrt{s}=200 GeV) in the central rapidity region including next-to-leading order, O(αemαs2)O(\alpha_{em}\alpha_s^2), radiative corrections, initial state nuclear shadowing and parton energy loss effects. We show that there is a significant suppression of the nuclear cross section, up to 30\sim 30% at s=200\sqrt{s}=200 GeV, due to shadowing and medium induced parton energy loss effects. We find that the next-to-leading order contributions are large and have a strong ptp_t dependence.Comment: 9 pages, 5 figures, expanded discussion of the K facto
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