We present a new approach to determining the strong coupling αs(Q), over the entire range of validity of perturbative QCD, for scales above ΛQCD and up to the Planck scale ∼1.22·1019 GeV, with the highest precision and using the data of a single experiment. In particular, we use the results obtained for the thrust (T) and C-parameter (C) distributions in e+e− annihilation at a single annihilation energy s=MZ (i.e. at the Z0 peak). This new method is based on the intrinsic conformality (iCF) and on the Infinite-Order Scale Setting, using the Principle of Maximum Conformality (i.e. the PMC∞), which allows a rigorous determination of the renormalization scales for the event-shape variable distributions satisfying all of the requirements of Renormalization Group Invariance, including renormalization-scheme independence and consistency with Abelian theory in the NC→0 limit. This new method is based on the scale-invariance of the iCF, which allows determination of αs(μ0) at any scale μ0, and on the Maximum Likelihood statistical approach. We propose a novel approach to determining the best-fitting range by considering all possible intervals over the entire range of bins available in the perturbative region and selecting that which returns the most-likely-lowest χmin2. This new method is designed to eliminate the errors that arise due to selection of the bin-interval and that have been neglected in previous analyses. In particular, using data for thrust and C-parameter at the Z0 peak from ALEPH, OPAL, DELPHI and L3 experiments, we obtain the average value: αs(MZ)=0.1182−0.0007+0.0007, for the strong coupling. This determination of αs(MZ) is consistent with the world average and has an improved precision with respect to the values obtained from the analysis of event shape observables currently used in the world average.
Scheme-independent determination of the QCD running coupling at all scales from jet observables using the principle of maximum conformality and infinite-order scale setting
Di Giustino L.;Ratcliffe P. G.;
2025-01-01
Abstract
We present a new approach to determining the strong coupling αs(Q), over the entire range of validity of perturbative QCD, for scales above ΛQCD and up to the Planck scale ∼1.22·1019 GeV, with the highest precision and using the data of a single experiment. In particular, we use the results obtained for the thrust (T) and C-parameter (C) distributions in e+e− annihilation at a single annihilation energy s=MZ (i.e. at the Z0 peak). This new method is based on the intrinsic conformality (iCF) and on the Infinite-Order Scale Setting, using the Principle of Maximum Conformality (i.e. the PMC∞), which allows a rigorous determination of the renormalization scales for the event-shape variable distributions satisfying all of the requirements of Renormalization Group Invariance, including renormalization-scheme independence and consistency with Abelian theory in the NC→0 limit. This new method is based on the scale-invariance of the iCF, which allows determination of αs(μ0) at any scale μ0, and on the Maximum Likelihood statistical approach. We propose a novel approach to determining the best-fitting range by considering all possible intervals over the entire range of bins available in the perturbative region and selecting that which returns the most-likely-lowest χmin2. This new method is designed to eliminate the errors that arise due to selection of the bin-interval and that have been neglected in previous analyses. In particular, using data for thrust and C-parameter at the Z0 peak from ALEPH, OPAL, DELPHI and L3 experiments, we obtain the average value: αs(MZ)=0.1182−0.0007+0.0007, for the strong coupling. This determination of αs(MZ) is consistent with the world average and has an improved precision with respect to the values obtained from the analysis of event shape observables currently used in the world average.
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