A measurement of the QCD colour factors and a limit on the light gluino

R. Barate, D. Buskulic, D. Decamp, P. Ghez, C. Goy, J. P. Lees, A. Lucotte, M. N. Minard, J. Y. Nief, P. Odier, B. Pietrzyk, M. P. Casado, M. Chmeissani, P. Comas, J. M. Crespo, M. Delfino, E. Fernandez, M. Fernandez-Bosman, Ll Garrido, A. JusteM. Martinez, R. Miquel, Ll M. Mir, S. Orteu, C. Padilla, I. C. Park, A. Pascual, J. A. Perlas, I. Riu, F. Sanchez, F. Teubert, A. Colaleo, D. Creanza, M. De Palma, G. Gelao, G. Iaselli, G. Maggi, M. Maggi, N. Marinelli, 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, R. Alemany, A. O. Bazarko, P. Bright-Thomas, M. Cattaneo, F. Cerutti, H. Drevermann, R. W. Forty, M. Frank, R. Hagelberg, J. Harvey, P. Janot, B. Jost, E. Kneringer, J. Knobloch, I. Lehraus, G. Lutters, P. Mato, A. Minten, L. Moneta, A. Pacheco, J. F. Pusztaszeri, F. Ranjard, P. Rensing, G. Rizzo, L. Rolandi, D. Schlatter, M. Schmelling, M. Schmitt, O. Schneider, W. Tejessy, I. R. Tomalin, H. Wachsmuth, A. Wagner, Z. Ajaltouni, A. Barrès, C. Boyer, A. Falvard, C. Ferdi, P. Gay, C. Guicheney, P. Henrard

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51 Citations (Scopus)

Abstract

Using data collected from 1992 to 1995 with the ALEPH detector at LEP, a measurement of the colour factor ratios CA/CF and TF/CF and the strong coupling constant ᾱs = CFαs(MZ)/(2π) has been performed by fitting theoretical predictions simultaneously to the measured differential two-jet rate and angular distributions in four-jet events. The result is found to be in excellent agreement with QCD, CA/CF = 2.20 ± 0.09 (stat) ± 0.13 (syst), TF/CF = 0.29 ± 0.05 (stat) ± 0.06 (syst). Fixing CA/CF and TF/CF to the QCD values permits a determination of αs(MZ) and nf, the number of active flavours. With this measurement the existence of a gluino with mass below 6.3 GeV/c2 is excluded at 95% confidence level. © Springer-Verlag 1997.
Original languageEnglish
Pages (from-to)1-14
JournalZeitschrift fur Physik C-Particles and Fields
Volume76
Issue number1
Publication statusPublished - 1 Sep 1997

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