The measurement of alpha_s from event shapes with the DELPHI detector at the highest LEP energies

TL;DR

This paper measures the strong coupling constant alpha_s using event shape data from e+e- collisions at high energies, applying advanced theoretical models and corrections to test its energy dependence.

Contribution

It provides a novel combined measurement of alpha_s across a wide energy range using multiple theoretical approaches and correction methods.

Findings

Consistent alpha_s values across different energies support QCD predictions.

The combined alpha_s measurement aligns with world averages.

The study tests the energy dependence of alpha_s with high precision.

Abstract

Hadronic event shape distributions are determined from data in e+e- collisions between 183 and 207 GeV. From these the strong coupling alpha_s is extracted in O(alpha_s^2), NLLA and matched O(alpha_s^2)+NLLA theory. Hadronisation corrections evaluated with fragmentation model generators as well as an analytical power ansatz are applied. Comparing these measurements to those obtained at and around M_Z allows a combined measurement of alpha_s from all DELPHI data and a test of the energy dependence of the strong coupling.