Precise determination of the strong coupling constant at NNLO in QCD from the three-jet rate in electron--positron annihilation at LEP

TL;DR

This paper provides a highly precise measurement of the strong coupling constant alpha_s at the Z boson mass scale using NNLO QCD predictions fitted to three-jet rate data from LEP, with minimal non-perturbative effects.

Contribution

First determination of alpha_s from three-jet rate in e+e- annihilation at NNLO accuracy, demonstrating improved precision and stability over previous methods.

Findings

Alpha_s(MZ) = 0.1175 +/- 0.0020 (exp) +/- 0.0015 (theo)

Small non-perturbative corrections over a large ycut range

Excellent stability under renormalisation scale variation

Abstract

We present the first determination of the strong coupling constant from the three-jet rate in e+e- annihilation at LEP, based on a next-to-next-to-leading order (NNLO) perturbative QCD prediction. More precisely, we extract alpha_s by fitting perturbative QCD predictions at O(alpha_s^3) to data from the ALEPH experiment at LEP. Over a large range of the jet-resolution parameter ycut this observable is characterised by small non-perturbative corrections and an excellent stability under renormalisation scale variation. For the three-jet rate at ln(ycut) = -3.9 we find alpha_s(MZ) = 0.1175 +/- 0.0020(exp) \+/- 0.0015(theo), which is among the most precise determinations from jet observables at LEP.