Abstract
We use a new compilation of the hadronic RR-ratio from available data for the process e^+e^-\toe+e−→ hadrons below the charm mass to determine the strong coupling \alpha_sαs, using finite-energy sum rules. Quoting our results at the \tauτ mass to facilitate comparison to the results obtained from similar analyses of hadronic \tauτ-decay data, we find \alpha_s(m_\tau^2)=0.298\pm 0.016\pm 0.006αs(mτ2)=0.298±0.016±0.006 in fixed-order perturbation theory, and \alpha_s(m_\tau^2)=0.304\pm 0.018\pm 0.006αs(mτ2)=0.304±0.018±0.006 in contour-improved perturbation theory, where the first error is statistical, and the second error combines various systematic effects. These values are in good agreement with a recent determination from the OPAL and ALEPH data for hadronic \tauτ decays. We briefly compare the R(s)R(s)-based analysis with the \tauτ-based analysis.
Highlights
New compilations of data for the R-ratio R(s), measured in the process e+e− → hadrons(γ), have appeared, mostly motivated by the aim to improve the dispersive prediction for the1.0 s GeV2 s GeV2hadronic vacuum polarization part of the muon anomalous magnetic moment [1,2,3]
As R(s) is directly proportional to the electromagnetic (EM) QCD vector spectral function, it gives access to other QCD quantities of interest. One of those is the strong coupling αs, which can be extracted from R(s) using finite-energy sum rules (FESRs) to the extraction of αs from the QCD spectral functions measured in hadronic τ decays
The extraction of αs from R(s) is interesting because it provides us with an alternative determination of the strong coupling from data at relatively low energies, providing another direct test of the running of the strong coupling as predicted by perturbation theory
Summary
New compilations of data for the R-ratio R(s), measured in the process e+e− → hadrons(γ), have appeared, mostly motivated by the aim to improve the dispersive prediction for the. As R(s) is directly proportional to the electromagnetic (EM) QCD vector spectral function, it gives access to other QCD quantities of interest One of those is the strong coupling αs, which can be extracted from R(s) using finite-energy sum rules (FESRs) to the extraction of αs from the QCD spectral functions measured in hadronic τ decays. The extraction of αs from R(s) is interesting because it provides us with an alternative determination of the strong coupling from data at relatively low energies, providing another direct test of the running of the strong coupling as predicted by perturbation theory. It can directly be compared with the determination from hadronic τ decays. We give a brief overview of the determination of αs from R(s), summarizing Ref. [4], to which we refer for details
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