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

R Barate; D Buskulic; D Decamp; P Ghez; C Goy; JP Lees; A Lucotte; MN Minard; JY Nief; P Odier; B Pietrzyk; MP Casado; M Chmeissani; P Comas; JM Crespo; M Delfino; E Fernandez; M Fernandez-Bosman; L Garrido; A Juste; M Martinez; R Miquel; LM Mir; S Orteu; C Padilla; IC Park; A Pascual; JA 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; AO Bazarko; P Bright-Thomas; M Cattaneo; F Cerutti; H Drevermann; RW 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; JF Pusztaszeri; F Ranjard; P Rensing; G Rizzo; L Rolandi; D Schlatter; M Schmelling; M Schmitt; O Schneider; W Tejessy; IR Tomalin; H Wachsmuth; A Wagner; Z Ajaltouni; A Barrès; C Boyer; A Falvard; C Ferdi; P Gay; C Guicheney; P Henrard

Journal article

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

R Barate, D Buskulic, D Decamp, P Ghez, C Goy, JP Lees, A Lucotte, MN Minard, JY Nief, P Odier, B Pietrzyk, MP Casado, M Chmeissani, P Comas, JM Crespo, M Delfino, E Fernandez, M Fernandez-Bosman, L Garrido, A Juste Show all

Zeitschrift fur Physik C-Particles and Fields | Published : 1997

DOI: 10.1007/s002880050522

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 ..

View full abstract