12,652 research outputs found
Determination of alpha_s from F_2^p at HERA
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
As any etymologist knows, the word âtextâ is derived from the past participle of the Latin verb texere, to weave. Text is therefore something that is âwovenâ. Itâs 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
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
We show that the double asymptotic scaling of the HERA structure function
data is consistent with pre-HERA data at larger , soft pomeron behaviour at
small and a sensible starting scale . We can thus actually calculate
at small and large 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
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
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
- âŚ