Engineering topics
Publications and source records attributed to Peris, Santiago.
We present a brief summary of our recent determination of αs from e + e - → hadrons, in the region 3 ≤ s ≤ 4 GeV 2 , with s the square of the center-of-mass energy.
We review how the current precision attained in the extraction of $α_s(m_τ)$ from hadronic $τ$ decays requires the inclusion of Duality Violations (DVs) in the analysis, even though these decays are largely dominated by perturbation theory. A weighted average using the OPAL and ALEPH experimental data yields $αs(m_Z) =$ 0.1165$±$0.0012 and $αs(m_Z) =$ 0.1185$±$0.0015 in fixed-orderand contour-improved perturbation theory, respectively.
We discuss sum-rule determinations of \alpha_s α s from non-strange hadronic \tau τ -decay data. We investigate, in particular, the reliability of the assumptions underlying the “truncated OPE strategy,” which specifies a certain treatment of non-perturbative contributions, and which was employed in Refs. . Here, we test this strategy by applying the strategy to the R R -ratio obtained from e^+e^- e + e − data, which extend beyond the \tau τ mass, and demonstrate that the assumptions underlying this strategy are not, in general, valid. We then present a brief overview of new results on the form of duality-violating non-perturbative contributions, which are conspicuously present in the experimentally determined spectral functions. As we show, with the current precision claimed for the extraction of \alpha_s α s , including a representation of duality violations is unavoidable if one wishes to avoid uncontrolled theoretical errors.
We use a new compilation of the hadronic R R -ratio from available data for the process e^+e^-\to e + e − → hadrons below the charm mass to determine the strong coupling \alpha_s α s , using finite-energy sum rules. Quoting our results at the \tau τ mass to facilitate comparison to the results obtained from similar analyses of hadronic \tau τ -decay data, we find \alpha_s(m_\tau^2)=0.298\pm 0.016\pm 0.006 α s ( m τ 2 ) = 0.298 ± 0.016 ± 0.006 in fixed-order perturbation theory, and \alpha_s(m_\tau^2)=0.304\pm 0.018\pm 0.006 α s ( m τ 2 ) = 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 \tau τ decays. We briefly compare the R(s) R ( s ) -based analysis with the \tau τ -based analysis.