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Persistent URL http://purl.org/net/epubs/work/29677
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Record Id 29677
Title Quantum Chromodynamics with the OPAL Detector at LEP
Abstract Quantum Chromodynamics is the study of the interactions of the strong force, which is one of the 3 forces in the Standard Model. I have studied several properties of the hadronic final states of e(+)e(-) annihilations with the OPAL detector. The OPAL detector is one of the four detectors on the LEP ring at CERN. As a nearly 4pi detector OPAL can fully reconstruct the hadronic final states of the e(+)e(-) collisions. Two matrix based methods for correcting the resolution and efficiency effects of the detector are compared. One of the methods is based upon the singular value decomposition of a matrix and the other is based upon Bayes' theorem. Both of the methods can reconstruct the underlying distribution from a measured distribution and an estimate of the detector effects. A measurement of the longitudinal cross-section for the decay of Z(0) --> hadrons is made, giving the result sigma(L)/sigma(tot)=0.0127+/-0.0016+/-0.0017. This measurement can be used with a theoretical calculation of longitudinal cross-section to measure a value of the strong coupling, alpha(s)(M(Z(0)))=0.126+/-0.016+/-0.017. The OPAL data for LEP 1 (sqrt(s)=M(Z(0))) and LEP 2 (sqrt(s)=161, 172 and 183 GeV) are used to measure some of the event shape distributions at these energies. The distributions and their moments, at LEP 1, or their means, widths and skewnesses, at LEP 2, are presented. These measurements are compared with several Monte Carlo models. These models show good agreement with the data at all of the energies. The data are also fitted to combined O(alpha(s)(2))+NLLA calculations of the event shape distributions. These are used to fit for the value of the strong coupling giving alpha(s)(M(Z(0)))=0.1150(+0.0075)(-0.0065), when fitted for 5 event shapes at 4 energies simultaneously. The possibility of a fixed value for the strong coupling can be excluded at the 96% confidence level.
Organisation CCLRC
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Language English (EN)
Type Details URI(s) Local file(s) Year
Thesis RAL Theses RAL-TH-1998-007. 1998. 1998