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Measurement of αs from the structure of particle clusters produced in hadronic Z decays

Research output: Contribution to journalJournal article


Journal publication date1991
JournalPhysics Letters B
Number of pages13
Original languageEnglish


Using 106 000 hadronic events obtained with the ALEPH detector at LEP at energies close to the Z resonance peak, the strong coupling constant αs is measured by an analysis of energy-energy correlations (EEC) and the global event shape variables thrust, C-parameter and oblateness. It is shown that the theoretical uncertainties can be significantly reduced if the final state particles are first combined in clusters using a minimum scaled invariant mass cut, Ycut, before these variables are computed. The combined result from all shape variables of pre-clustered events is αs(MZ2 = 0.117±0.005 for a renormalization scale . For μ values between MZ and the b-quark mass, the result changes by −0.009+0.006.