12,652 research outputs found

    Determination of alpha_s from F_2^p at HERA

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    We compute the proton structure function F_2^p at small x and large Q^2 at next-to-leading order in alpha_s(Q^2), including summations of all leading and subleading logarithms of Q^2 and 1/x in a way consistent with momentum conservation. We perform a detailed comparison to the 1993 HERA data, and show that they may be used to determine alpha_s(M_Z^2)=0.120 pm 0.005(exp) pm 0.009(th). The theoretical error is dominated by the renormalization and factorization scheme ambiguities.Comment: 24 pages, TeX with harvmac and epsf, 10 figures in compressed postscript. Final (published) versio

    The Pleating of History: Weaving the Threads of Nationhood

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    As any etymologist knows, the word ‘text’ is derived from the past participle of the Latin verb texere, to weave. Text is therefore something that is ‘woven’. It’s a persuasive metaphor, to imagine writing in terms of the warp and weft of ideas and words, of narrative threads woven together to become a piece of fabric. The idea of history as fabric brings together a whole different set of tropes, not just of weaving, but of the very materiality of fabric. Does the fabric have a nap, or a pattern? Is it cut with the grain, or on the bias? What of its folds, its seams? All these qualities of fabric have application in the interpretation of history, and some of these images are already familiar in historical discourse

    Asymptotically Free Partons at High Energy

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    We describe the application of renormalization group improved perturbative QCD to inelastic lepton-hadron scattering at high center-of-mass energy but comparatively low photon virtuality. We construct a high energy factorization theorem which complements the mass factorization theorem used for processes with high virtualities. From it we derive a renormalization group equation which resums all large logarithms at high energy, thereby extending to this regime asymptotic freedom and thus the full range of perturbative computational techniques. We discuss the solution of this equation in various limits, and in particular show that the high energy behaviour of physical cross-sections is consistent with phenomenological expectations and unitarity bounds.Comment: 16 pages, TeX with harvmac, 6 figures in encapsulated postscript, final versio

    Calculating F_2^p at small x and large Q^2

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    We show that the double asymptotic scaling of the HERA structure function data is consistent with pre-HERA data at larger xx, soft pomeron behaviour at small xx and a sensible starting scale Q0Q_0. We can thus actually calculate F2pF_2^p at small xx and large Q2Q^2 by evolving up perturbatively at two loops, without any fitting.Comment: 7 pages, TeX with harvmac, 4 figures in compressed postscript, CERN-TH.7422/9

    Towards the improvement of self-service systems via emotional virtual agents

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    Affective computing and emotional agents have been found to have a positive effect on human-computer interactions. In order to develop an acceptable emotional agent for use in a self-service interaction, two stages of research were identified and carried out; the first to determine which facial expressions are present in such an interaction and the second to determine which emotional agent behaviours are perceived as appropriate during a problematic self-service shopping task. In the first stage, facial expressions associated with negative affect were found to occur during self-service shopping interactions, indicating that facial expression detection is suitable for detecting negative affective states during self-service interactions. In the second stage, user perceptions of the emotional facial expressions displayed by an emotional agent during a problematic self-service interaction were gathered. Overall, the expression of disgust was found to be perceived as inappropriate while emotionally neutral behaviour was perceived as appropriate, however gender differences suggested that females perceived surprise as inappropriate. Results suggest that agents should change their behaviour and appearance based on user characteristics such as gender

    HERA data and DGLAP evolution: theory and phenomenology

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    We examine critically the evidence for deviations from next-to-leading order perturbative DGLAP evolution in HERA data. We briefly review the status of perturbative small-x resummation and of global determinations of parton distributions. We show that the geometric scaling properties of HERA data are consistent with DGLAP evolution, which is also strongly supported by the double asymptotic scaling properties of the data. However, backward--evolution of parton distributions into the low x, low Q^2 region does show evidence of deviations between the observed behaviour and the next-to-leading order predictions. These deviations cannot be explained by missing next-to-next-to-leading order perturbative terms, and are consistent with perturbative small-x resummation.Comment: Fig. 8 corrected. Published in NP
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