NLO QCD corrections to five-jet production at LEP and the extraction of α_s(M_Z)

The highest exclusive jet multiplicity studied at LEP experiments is five. In this paper we compute the next-to-leading order QCD corrections to e ⁺e^- annihilation to five jets, essentially closing the (pure) perturbative QCD studies of exclusive jetty final states at LEP. We compare fixed-order perturbative results with ALEPH data. We estimate hadronization corrections to five-jet observables using the event generator SHERPA, which employs the CKKW procedure to combine a reliable perturbative treatment of highmultiplicity jet final states with parton showers. We show that a competitive value of the strong coupling constant α_s(M _Z) = 0.1156_-0.0034^+0.0041 can be extracted from the distribution of the five-jet resolution parameter and the five-jet rate at LEP1 and LEP2.