The ALEPH collaboration: Measurements of the strong coupling constant and the QCD colour factors using four-jet observables from hadronic Z decays

A. Heister, S. Schael, R. Barate, I. De Bonis, D. Decamp, C. Goy, J. P. Lees, E. Merle, M. N. Minard, B. Pietrzyk, G. Boix, S. Bravo, M. P. Casado, M. Chmeissani, J. M. Crespo, E. Fernandez, M. Fernandez-Bosman, L. Garrido, E. Graugés, M. MartinezG. Merino, R. Miquel, L. M. Mir, A. Pacheco, H. Ruiz, A. Colaleo, D. Creanza, M. de Palma, G. Iaselli, G. Maggi, M. Maggi, S. Nuzzo, A. Ranieri, G. Raso, F. Ruggieri, G. Selvaggi, L. Silvestris, P. Tempesta, A. Tricomi, G. Zito, X. Huang, J. Lin, Q. Ouyang, T. Wang, Y. Xie, R. Xu, S. Xue, J. Zhang, L. Zhang, W. Zhao, D. Abbaneo, P. Azzurri, O. Buchmüller, M. Cattaneo, F. Cerutti, B. Clerbaux, H. Drevermann, R. W. Forty, M. Frank, F. Gianotti, T. C. Greening, J. B. Hansen, J. Harvey, D. E. Hutchcroft, P. Janot, B. Jost, M. Kado, P. Mato, A. Moutoussi, F. Ranjard, L. Rolandi, D. Schlatter, O. Schneider, G. Sguazzoni, W. Tejessy, F. Teubert, A. Valassi, I. Videau, J. Ward, F. Badaud, A. Falvard, P. Gay, P. Henrard, J. Jousset, B. Michel, S. Monteil, J. C. Montret, D. Pallin, P. Perret, J. D. Hansen, J. R. Hansen, P. H. Hansen, B. S. Nilsson, A. Kyriakis, C. Markou, E. Simopoulou, A. Vayaki, K. Zachariadou, A. Blondel, G. Bonneaud

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27 Citations (Scopus)

Abstract

Data from e+e- annihilation into hadrons, taken with the ALEPH detector at the Z resonance, are analyzed. The four-jet rate is studied as a function of the resolution parameter and compared to next-to-leading order calculations combined with resummation of large logarithms. Angular correlations in four-jet events are measured and compared to next-to-leading order QCD predictions. With these observables two different measurements are performed. In a first analysis the strong coupling constant is measured from the four-jet rate yielding αs(MZ) = 0.1170 ± 0.0001 (stat) ± 0.0013(sys). In a second measurement the strong coupling constant and the QCD colour factors are determined simultaneously from a fit to the four-jet rate and the four-jet angular correlations, giving αs(MZ) = 0.119 ± 0.006(stat) ± 0.026(sys) CA = 2.93 ± 0.14(stat) ± 0.58(sys) CF = 1.35 ± 0.07(stat) ± 0.26(sys) in good agreement with the expectation from QCD.
Original languageEnglish
Pages (from-to)1-17
JournalEuropean Physical Journal C
Volume27
Issue number1
Publication statusPublished - 1 Jan 2003

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