2,283 research outputs found

    Impact of QED corrections to Higgs decay into four leptons at the LHC

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    At the LHC a precise measurement of the Higgs boson mass (if discovered), at the level of 0.1-1%, will be possible through the channel g g --> H --> 4l for a wide range of Higgs mass values. To match such an accuracy, the systematic effects induced by QED corrections need to be investigated. In the present study the calculation of O(alpha) and higher order QED corrections is illustrated as well as their impact on the Higgs mass determination, once realistic event selection criteria for charged leptons and photons are considered.Comment: 5 pages, 5 figures, 1 table. Presented at HEP2005 July 21st-27th, 2005, Lisboa, Portugal and at RADCOR 2005, Shonan Village, October 2nd-7th, 2005, Japa

    Photon pair production at flavour factories with per mille accuracy

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    We present a high-precision QED calculation, with 0.1% theoretical accuracy, of two photon production in e+ee^+ e^- annihilation, as required by more and more accurate luminosity monitoring at flavour factories. The accuracy of the approach, which is based on the matching of exact next-to-leading order corrections with a QED Parton Shower algorithm, is demonstrated through a detailed analysis of the impact of the various sources of radiative corrections to the experimentally relevant observables. The calculation is implemented in the latest version of the event generator BabaYaga, available for precision simulations of photon pair production at e+ee^+ e^- colliders of moderately high energies.Comment: 11 pages, 5 figures, 1 tabl

    Precision electroweak calculation of the production of a high transverse-momentum lepton pair at hadron colliders

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    We present a detailed study of the production of a high transverse-momentum lepton pair at hadron colliders, which includes the exact O(alpha) electroweak corrections properly matched with leading logarithmic effects due to multiple photon emission, as required by the experiments at the Fermilab Tevatron and the CERN LHC. Numerical results for the relevant observables of single Z-boson production at hadron colliders are presented. The impact of the radiative corrections is discussed in detail. The presence in the proton of a photon density is considered and the effects of the photon-induced partonic subprocesses are analyzed. The calculation has been implemented in the new version of the event generator HORACE, which is available for precision simulations of the neutral and charged current Drell-Yan processes.Comment: October 2007, 22p

    MicroRNA-155 Function in B Cells

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    Vigorito et al. (2007) report (in this issue of Immunity) that B cells require microRNA (miR)-155 for normal production of isotype-switched, high-affinity antibodies and for a memory response. They identify transcriptional regulator Pu.1 as a functionally important target of miR-155 in B cells

    Post-war Reconstruction: Concerns, Models and Approaches

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    This article focuses on constructive critique, recognition of avoidable mistakes, and speculation about viable, large-scale post-war reconstruction projects. The ideal outcome would be identification of such a project, suitable for near-term implementation, that could illuminate existing best practices along with innovative new approaches to an old proble

    Bug Hunting with False Negatives Revisited

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    Safe data abstractions are widely used for verification purposes. Positive verification results can be transferred from the abstract to the concrete system. When a property is violated in the abstract system, one still has to check whether a concrete violation scenario exists. However, even when the violation scenario is not reproducible in the concrete system (a false negative), it may still contain information on possible sources of bugs. Here, we propose a bug hunting framework based on abstract violation scenarios. We first extract a violation pattern from one abstract violation scenario. The violation pattern represents multiple abstract violation scenarios, increasing the chance that a corresponding concrete violation exists. Then, we look for a concrete violation that corresponds to the violation pattern by using constraint solving techniques. Finally, we define the class of counterexamples that we can handle and argue correctness of the proposed framework. Our method combines two formal techniques, model checking and constraint solving. Through an analysis of contracting and precise abstractions, we are able to integrate overapproximation by abstraction with concrete counterexample generation

    Multi-photon corrections to W boson mass determination at hadron colliders

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    The impact of higher-order final-state photonic corrections on the precise determination of the W-boson mass at the Tevatron and LHC colliders is evaluated. The W-mass shift from a fit to the transverse mass distribution is found to be about 10 MeV in the W --> mu nu channel and a few MeV in the W --> e nu channel. The calculation, which is implemented in the Monte Carlo event generator HORACE for data analysis, can contribute to reduce the uncertainty associated to the W mass measurement at present and future hadron collider experiments.Comment: 3 pages, 2 figures, to appear in the proceedings of International Europhysics Conference on High-Energy Physics (EPS 2003), Aachen, Germany, 17-23 Jul 200
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