3,992 research outputs found

    Combining QCD Matrix Elements and Parton Showers

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    A new method for combining QCD matrix elements and parton showers in Monte Carlo simulations of hadronic final states is outlined. The aim is to provide at least a leading-order description of all hard multi-jet configurations together with jet fragmentation to next-to-leading logarithmic accuracy, while avoiding the most serious problems of double counting.Comment: 6 pages, 8 figures. Talk at XXXV Rencontres de Moriond, Les Arcs, France, March 200

    Fragmentation and Hadronization

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    Experimental data, theoretical ideas and models concerning jet fragmentation and the hadronization process are reviewed, concentrating on the following topics: factorization and small-x resummation of fragmentation functions, hadronization models, single-particle yields and spectra in Z decay, comparisons between quark and gluon jets, current and target fragmentation in deep inelastic scattering, heavy quark fragmentation, Bose-Einstein correlations and WW fragmentation.Comment: 31 pages, 33 figures. Plenary talk at XIX International Symposium on Lepton and Photon Interactions at High Energies, Stanford, August 199

    The MC@NLO 3.2 Event Generator

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    This is the user's manual of MC@NLO 3.2. This package is a practical implementation, based upon the HERWIG event generator, of the MC@NLO formalism, which allows one to incorporate NLO QCD matrix elements consistently into a parton shower framework. Processes available in this version include the hadroproduction of single vector and Higgs bosons, vector boson pairs, heavy quark pairs, single top, lepton pairs, and Higgs bosons in association with a W or Z. Spin correlations in decays are included for all processes except ttbar, single-t, ZZ, and WZ production. This document is self-contained, but we emphasise the main differences with respect to previous versions.Comment: 23 pages Late

    QCD Scaling Violation at Small x

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    We investigate the evolution of parton densities at small values of the momentum fraction, x, by including resummed anomalous dimensions in the renormalization group equations. The resummation takes into account the leading-logarithmic contributions (\alpha_S \ln x)^k given by the BFKL equation and the next-to-leading-logarithmic corrections from quark evolution. We present numerical results for the parton densities and the deep inelastic structure function F_2.Comment: 8 pages, Latex, 3 uuencoded figure

    Power Corrections to Fragmentation Functions in Non-Singlet Deep Inelastic Scattering

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    We investigate the power-suppressed corrections to the fragmentation functions of the current jet in non-singlet deep inelastic lepton-hadron scattering. The current jet is defined by selecting final-state particles in the current hemisphere in the Breit frame of reference. Our method is based on an analysis of one-loop Feynman graphs containing a massive gluon, which is equivalent to the evaluation of leading infrared renormalon contributions. We find that the leading corrections are proportional to 1/Q21/Q^2, as in e+e−e^+e^- annihilation, but their functional forms are different. We give quantitative estimates based on the hypothesis of universal low-energy behaviour of the strong coupling.Comment: 14 pages, 4 figures, LaTeX2e, uses JHEP.cls (included) and epsfi