How to continue the predictions of perturbative QCD from the spacelike region where they are derived to the timelike regime where experiments are performed |
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Authors: | MR Pennington RG Roberts GG Ross |
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Institution: | 1. Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, UK |
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Abstract: | The predictions of perturbative QCD are derived in the deep euclidean region, whereas the physical region for most observables is timelike. The confrontation of these predictions with experiment thus necessitates an analytic continuation. This we find introduces large higher order corrections in terms of αs(|Q2|), the usual choice ofperturbative expansion parameter. These corrections are naturally absorbed by changing to the expansion parameter , where αs(Q2)n is the leading term in the spacelike region. For the intermediate range of Q2 experimentally accessible at present, where is significantly smaller than αs(|Q2|), we find the resulting phenomenology is improved. In particular, we demonstrate how the values of obtained from analyses of quarkonium decays become consistent. |
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