812 research outputs found

    Perturbative Evolution and Regge Behaviour

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    The known analytic properties of the Compton amplitude at small Q2Q^2 place significant constraints on its behaviour at large Q2Q^2. This calls for a re-evaluation of the role of perturbative evolution in past fits to data.Comment: Revised figures 4 and

    Soft and hard pomerons

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    Regge theory provides an excellent description of small-xx structure-function data from Q2=0Q^2=0 up to the highest available values. The large-Q2Q^2 data should also be described by perturbative QCD: the two descriptions must agree in the region where they overlap. However, at present there is a serious lack in our understanding of how to apply perturbative QCD at small xx. The usual lowest-order or next-to-lowest order expansion is not valid, at least not until Q2Q^2 becomes much larger than is usually assumed; a resummation is necessary, but as yet we do not know how to do this resummation.Comment: 8 pages, plain tex, with 6 figures embedded using epsf. Lecture at Workshop on New Trends in HERA Physics, Ringberg (june 1999

    Unusual high-pT jet events at HERA

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    We calculate the cross-section for events at HERA where the proton loses only a minute fraction of its initial energy, all of which goes into producing a single pair of transverse jets.Comment: 4 pages plus figure
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