Determination of alpha_s using Jet Rates at LEP with the OPAL detector

TL;DR

This paper measures the strong coupling constant alpha_s at LEP energies using jet rate distributions from e+e- collisions recorded by the OPAL detector, employing multiple jet algorithms and theoretical predictions for precise determination.

Contribution

It introduces a comprehensive analysis of jet rates with four algorithms to extract alpha_s, combining data across energies and matching NLLA predictions with experimental results.

Findings

Measured alpha_s(Mz) = 0.1177 ± 0.0006 (stat) ± 0.0012 (expt) ± 0.0010 (had) ± 0.0032 (theo)

Used multiple jet algorithms to ensure robustness of alpha_s extraction

Provided a precise determination of alpha_s consistent with the Standard Model

Abstract

Hadronic events produced in e+e- collisions by the LEP collider and recorded by the OPAL detector were used to form distributions based on the number of reconstructed jets. The data were collected between 1995 and 2000 and correspond to energies of 91 GeV, 130-136 GeV and 161-209 GeV. The jet rates were determined using four different jet-finding algorithms (Cone, JADE, Durham and Cambridge). The differential two-jet rate and the average jet rate with the Durham and Cambridge algorithms were used to measure alpha(s) in the LEP energy range by fitting an expression in which order alpah_2s calculations were matched to a NLLA prediction and fitted to the data. Combining the measurements at different centre-of-mass energies, the value of alpha_s (Mz) was determined to be alpha(s)(Mz)=0.1177+-0.0006(stat.)+-0.0012$(expt.)+-0.0010(had.)+-0.0032(theo.) \.