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


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 ..

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