Abstract
We present state-of-the-art extractions of the strong coupling based on N3LO+NNLL accurate predictions for the two-jet rate in the Durham clustering algorithm at e+e− collisions, as well as a simultaneous fit of the two- and three-jet rates taking into account correlations between the two observables. The fits are performed on a large range of data sets collected at the LEP and PETRA colliders, with energies spanning from 35 GeV to 207 GeV. Owing to the high accuracy of the predictions used, the perturbative uncertainty is considerably smaller than that due to hadronization. Our best determination at the Z mass is αs (MZ) = 0.11881 ± 0.00063(exp.) ± 0.00101(hadr.) ± 0.00045(ren.) ± 0.00034(res.), which is in agreement with the latest world average and has a comparable total uncertainty.
Highlights
We present state-of-the-art extractions of the strong coupling based on N3LO+next-to-next-to-leading logarithms (NNLL) accurate predictions for the two-jet rate in the Durham clustering algorithm at e+e− collisions, as well as a simultaneous fit of the two- and three-jet rates taking into account correlations between the two observables
We focus on jet rates obtained with the Durham clustering algorithm [27] and will use for the first time NNLL predictions for the two-jet rate R2(y), which became available in ref. [20]
The main result of this paper is an extraction of the strong coupling from the Durham two-jet rate to data measured at the LEP and PETRA colliders which relies on N3LO+NNLL accurate theoretical predictions
Summary
A jet clustering algorithm is a procedure to classify final-state events into different jet multiplicities. This categorisation depends on the underlying algorithm used. Paper we adopt the Durham clustering [27] This is a sequential recombination algorithm, which requires a distance measure in phase space between momenta pμi and pμj , yij. If the smallest of these, ymin = min({yij}) is below a pre-defined number, ycut, the corresponding pair of momenta is recombined into a single one. We adopt the E-scheme [27], according to which the four-momenta of the two clustering particles are added together. Where σn-jet is the cross section for n-jet production in hadronic final states obtained with the above algorithm and σtot is the total hadronic cross section. The two results can be combined by means of a matching procedure to obtain the predictions that we use in the fit
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