Measurement of alpha_s(M_Z^2) from Hadronic Event Observables at the Z^0 Resonance

TL;DR

This paper measures the strong coupling constant alpha_s at the Z boson mass scale using various hadronic event observables from Z^0 decays, comparing data with QCD predictions and combining results for a precise determination.

Contribution

It provides a comprehensive analysis of alpha_s(M_Z^2) using multiple observables and advanced QCD calculations, improving the precision of the strong coupling measurement.

Findings

Measured alpha_s(M_Z^2) = 0.1200
0.0025 (exp.)
0.0078 (theor.)

Consistent alpha_s values obtained from different event shape and jet observables

Dominant uncertainty from uncalculated higher order QCD contributions

Abstract

The strong coupling alpha_s(M_Z^2) has been measured using hadronic decays of Z^0 bosons collected by the SLD experiment at SLAC. The data were compared with QCD predictions both at fixed order, O(alpha_s^2), and including resummed analytic formulae based on the next-to-leading logarithm approximation. In this comprehensive analysis we studied event shapes, jet rates, particle correlations, and angular energy flow, and checked the consistency between alpha_s(M_Z^2) values extracted from these different measures. Combining all results we obtain alpha_s(M_Z^2) = 0.1200 \pm 0.0025(exp.) \pm 0.0078(theor.), where the dominant uncertainty is from uncalculated higher order contributions.