A study of the recombination scheme dependence of jet production rates and of α _s ($M_{Z^0 }$) in hadronicZ ⁰ decays

Abstract

Jet production rates in hadronicZ ⁰ decays are studied using four different recombination schemes to define resolvable jets. The strong coupling constant α _s ($M_{Z^0 }$) is determined in fits of the correspondingO(α ² _s ) QCD calculations to the differential 2-jet distributionsD ₂(y). Hadronisation corrections and renormalisation scale uncertainties are found to be different for each recombination scheme. Within their overall systematic uncertainties, the four schemes yield consistent values of α _s ($M_{Z^0 }$), leading to a final result of

$$\alpha _s (M_{Z^0 } ) = 0.118 \pm 0.008.$$

.

The error includes the experimental uncertainties (±0.003), uncertainties of hadronisation corrections and of the degree of parton virtualities to which the data are corrected, as well as the uncertainty of choosing the renormalisation scale.