Determination of αs at LEP by L3 experiment

Abstract

The results on strong coupling constant, α s in e +e − collision at LEP are reviewed, based on hadronic events collected at centre-of-mass energies between 30 GeV and 208 GeV by the L3 experiment. In particularly the recent results at √s ≥ 192 GeV are discussed. The distributions of several event shape variables are compared to resummed O( α s 2) QCD calculations. These measurements, combined with previous L3 measurements at lower energies, demonstrate the running of α s as expected in QCD and yield α s( m Z ) = 0.1227 ± 0.0012 ± 0.0058, where the first uncertainty is experimental and the second is theoretical.