Eliminating the Renormalization Scale Ambiguity for Top-Pair Production Using the Principle of Maximum Conformality

Stanley J. Brodsky and Xing-Gang Wu
Phys. Rev. Lett. 109, 042002 – Published 23 July 2012

Abstract

It is conventional to choose a typical momentum transfer of the process as the renormalization scale and take an arbitrary range to estimate the uncertainty in the QCD prediction. However, predictions using this procedure depend on the renormalization scheme, leave a nonconvergent renormalon perturbative series, and moreover, one obtains incorrect results when applied to QED processes. In contrast, if one fixes the renormalization scale using the principle of maximum conformality (PMC), all nonconformal {βi} terms in the perturbative expansion series are summed into the running coupling, and one obtains a unique, scale-fixed, scheme-independent prediction at any finite order. The PMC scale μRPMC and the resulting finite-order PMC prediction are both to high accuracy independent of the choice of initial renormalization scale μRinit, consistent with renormalization group invariance. As an application, we apply the PMC procedure to obtain next-to-next-to-leading-order (NNLO) predictions for the tt¯-pair production at the Tevatron and LHC colliders. The PMC prediction for the total cross section σtt¯ agrees well with the present Tevatron and LHC data. We also verify that the initial scale independence of the PMC prediction is satisfied to high accuracy at the NNLO level: the total cross section remains almost unchanged even when taking very disparate initial scales μRinit equal to mt, 20mt, and s. Moreover, after PMC scale setting, we obtain AFBtt¯12.5%, AFBpp¯8.28% and AFBtt¯(Mtt¯>450GeV)35.0%. These predictions have a 1σ deviation from the present CDF and D0 measurements; the large discrepancy of the top quark forward-backward asymmetry between the standard model estimate and the data are, thus, greatly reduced.

  • Figure
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  • Received 29 March 2012

DOI:https://doi.org/10.1103/PhysRevLett.109.042002

© 2012 American Physical Society

Authors & Affiliations

Stanley J. Brodsky1,* and Xing-Gang Wu1,2,†

  • 1SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
  • 2Department of Physics, Chongqing University, Chongqing 401331, People’s Republic of China

  • *sjbth@slac.stanford.edu
  • wuxg@cqu.edu.cn

See Also

Application of the principle of maximum conformality to top-pair production

Stanley J. Brodsky and Xing-Gang Wu
Phys. Rev. D 86, 014021 (2012)

Self-consistency requirements of the renormalization group for setting the renormalization scale

Stanley J. Brodsky and Xing-Gang Wu
Phys. Rev. D 86, 054018 (2012)

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Vol. 109, Iss. 4 — 27 July 2012

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