A Study of Hadronic Final States in e+e- Annihilation at 44 GeV

High energy physics

McCurrach, Graham Munro

University:University of Glasgow

关键词: High energy physics;   

Others  :  http://theses.gla.ac.uk/77516/1/10995564.pdf

来源: University of Glasgow

【 摘 要 】

The analysis of multihadronic events resulting from the interaction of an electron and a positron has been carried out using the data obtained with the CELLO detector situated at the PETRA e+e- storage ring. There are 5605 events in the data sample which were acquired at an average beam energy of 22 GeV. These events were used to ascertain whether the hadronic data could be described by a candidate theory of the strong interaction; namely quantum chromodynamics. It is shown that quantum chromodynamics describes the main features of the data. The theoretical properties of the transition from quark and gluons to hadrons is discussed, and in particular, three models of fragmentation are discussed. The relative merits of the string model, the independent jet model and the cluster model were evaluated from an experimental viewpoint and on a theoretical basis. The string model of fragmentation was found to give the best agreement with the published experimental data. Using the string model of fragmentation, a value of aS, the strong interaction coupling constant, was obtained. This was done by statistically fitting the experimental corrected data to the theoretical quantum chromodynamic prediction. Various distributions were employed to determine as and their relative merits assessed. It was found that the energy energy correlation asymmetry provided the most accurate measure of the strong coupling constant, namely, aS(Q2 = 1936GeV2) = 0.152+/-0 .010(systematic) +/-0.01(statistical).