Analytic perturbation theory in analyzing some QCD observables

DOI10.1007/S100520100794zbMATH Open1071.81586arXivhep-ph/0107282OpenAlexW3100039181MaRDI QIDQ5952460

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Publication date: 9 January 2002

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Abstract: The paper is devoted to application of recently devised ghost-free Analytic Perturbation Theory (APT) for analysis of some QCD observables. We start with the discussion of the main problem of the perturbative QCD -- ghost singularities and with the resume of this trouble solution within the APT. By a few examples in the various energy and momentum transfer regions (with the flavor number f=3, 4 and 5) we demonstrate the effect of improved convergence of the APT modified perturbative QCD expansion. Our first observation is that in the APT analysis the three-loop contribution $simalph{a}_s^3$) is as a rule numerically inessential. This gives raise a hope for practical solution of the well-known problem of asymptotic nature of common QFT perturbation series. The second result is that a usual perturbative analysis of time-like events with the big $p{i}^2$ term in the $alph{a}_s^3$ coefficient is not adequate at $sleq2Ge{V}^2$. In particular, this relates to $au$ decay. Then, for the "high" (f=5) region it is shown that the common two-loop (NLO, NLLA) perturbation approximation widely used there (at $10GeVlesssimsqrtslesssim170GeV$) for analysis of shape/events data contains a systematic negative error of a 1--2 per cent level for the extracted $$ values. Our physical conclusion is that the $$ value averaged over the f=5 data appreciably differs $<bar{alpha}_s(M_Z^2){>}_{f=5}simeq0.124$ from the currently accepted "world average" (=0.118).}

Full work available at URL: https://arxiv.org/abs/hep-ph/0107282

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