223 research outputs found

    QED \otimes QCD Threshold Corrections at the LHC

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    We use the theory of YFS resummation to compute the size of the expected resummed soft radiative threshold effects in precision studies of heavy particle production at the LHC, where accuracies of 1 percent are desired in some processes. We find that the soft QED threshold effects are at the level of 0.3 percent whereas the soft QCD threshold effects enter at the level of 20 percent and hence both must be controlled to be on the conservative side to achieve such goals.Comment: 8 pages, no figures; improved text; improved refs. and tex

    The Virtual Correction to Bremsstrahlung in High-Energy e+ e- Annihilation: Comparison of Exact Results

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    We have compared the virtual corrections to single hard bremsstrahlung as calculated by S. Jadach, M. Melles, B.F.L. Ward and S.A. Yost to several other expressions. The most recent of these comparisons is to the leptonic tensor calculated by J.H. Kuhn and G. Rodrigo for radiative return. Agreement is found to within a part in 10^5 or better, as a fraction of the Born cross section, for most of the range of photon energies. The massless limits have been shown to agree analytically to NLL order.Comment: 7 pages, 2 figures. Presented by S.A. Yost at ICHEP 2004, International Conference on High Energy Physics, Beijing, August 16-22, 200

    Threshold Corrections in Precision LHC Physics: QED otimes QCD

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    With an eye toward LHC processes in which theoretical precisions of 1 percent are desired, we introduce the theory of the simultaneous YFS resummation of QED and QCD to compute the size of the expected resummed soft radiative threshold effects in precision studies of heavy particle production at the LHC. Our results show that both QED and QCD soft threshold effects must be controlled to be on the conservative side to achieve such precision goals.Comment: 4 pages, no figures; presented by B.F.L. Ward in DPF200

    New Results on Precision Studies of Heavy Vector Boson Physics

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    We present new results for two important heavy vector boson physics processes: (1), virtual corrections to hard bremsstrahlung which are relevant to precision predictions for the radiative return process in Z boson production at and beyond LEP2 energies ; and, (2), electric charge screening effects in single W production with finite p_T, multiple photon radiation in high energy collider physics processes. In both cases we show that we improve the respective precision tag significantly. Phenomenological implications are discussed.Comment: 5 pages, 2 figures; to appear in Proc. DPF200

    Differential Cross Sections for Higgs Production

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    We review recent theoretical progress in evaluating higher order QCD corrections to Higgs boson differential distributions at hadron-hadron colliders

    Comparison of Exact Results for the Virtual Corrections to Bremsstrahlung in Electron-Positron Annihilation at High Energies

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    We have compared the virtual corrections to electron-positron annihilation to fermion pairs with single hard bremsstrahlung as calculated by S. Jadach, M. Melles, B.F.L. Ward and S.A. Yost to several other expressions. The most recent of these comparisons is to the leptonic tensor calculated by J.H. Kuhn and G. Rodrigo for radiative return. Agreement is found to within 10−510^{-5} or better, as a fraction of the Born cross section.Comment: 5 pages, 2 figures. Presented at LCWS 2004, International Conference on Linear Colliders, Paris, April 19-23, 200

    Threshold Corrections in QED otimes QCD at the LHC

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    In some processes at the LHC, theoretical precisions of 1 percent are desired. With an eye toward such precisions, we introduce the theory of the simultaneous YFS resummation of QED and QCD to compute the size of the expected resummed soft radiative threshold effects in precision studies of heavy particle production at the LHC. Our results, that the soft QED threshold effects are at the level of 0.3 percent whereas the soft QCD threshold effects enter at the level of 20 percent, show that both must be controlled to be on the conservative side to achieve such precision goals.Comment: 4 pages, no figures; presented by B.F.L. Ward at ICHEP0

    Next-to-leading order predictions for WW + 1 jet distributions at the LHC

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    We present numerical results for the production of a W+W−W^+W^- pair in association with a jet at the LHC in QCD at next-to-leading order (NLO). We include effects of the decay of the massive vector bosons into leptons with spin correlations and contributions from the third generation of massive quarks. The calculation is performed using a semi-numerical method for the virtual corrections, and is implemented in MCFM. In addition to its importance {\it per se} as a test of the Standard Model, this process is an important background to searches for the Higgs boson and to many new physics searches. As an example, we study the impact of NLO corrections to W+W−+W^+W^-+ jet production on the search for a Higgs boson at the LHC.Comment: 21 pages, 9 figures; v3 published versio

    Resummed Quantum Gravity

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    We present the current status of the a new approach to quantum general relativity based on the exact resummation of its perturbative series as that series was formulated by Feynman. We show that the resummed theory is UV finite and we present some phenomenological applications as well.Comment: 4 pages, 1 figure; presented at ICHEP0
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