A Measurement of the Colour Factors of Quantum Chromodynamics From Four-Jet Events at LEP

[摘要] From a sample of 3.7 million events collected with the ALEPH detector between 1992 and 1995, those containing four jets are selected. These are used to measure angular variables sensitive to the underlying spin structure of the event which are then combined with O(alpha2s) QCD predictions to extract values of the Colour Factor ratios CA/CF and TR/CF. Events containing two identified b jets are separated from the rest of the data and the extra information used to increase the accuracy of the measurement. A matrix element calculation which takes the b quark mass into account is used in the fit to these tagged events. The final Colour Factor values are obtained by combining the results from the two samples: CA/CF= 2.294 +/-0.151 TR/CF =1.491 +/-0.490 which are in agreement with the QCD predictions of CA/CF= 2.25 and TR/CF= 1.875.

[发布机构] University:University of Glasgow

[关键词] High energy physics, Nuclear physics and radiation