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First determination of the electric charge of the top quark
KTH, School of Engineering Sciences (SCI), Physics.
2006 (English)Licentiate thesis, monograph (Other scientific)
Abstract [en]

In this thesis, the first determination of the electric charge of the top quark is presented using 370pb-1 of data recorded by the DØ detector at the Fermilab Tevatron accelerator. ttbar events are selected with one isolated electron or muon and at least four jets out of which two are b-tagged by reconstruction of a secondary decay vertex (SVT). The method is based on the discrimination between b- and b-quark jets using a jet charge algorithm applied to SVT-tagged jets. A method to calibrate the jet charge algorithm with data is developed. A constrained kinematic fit is performed to associate the W bosons to the correct b-quark jets in the event and extract the top quark electric charge. The data is in good agreement with the Standard Model top quark electric charge of 2e/3. The scenario where the selected sample is solely composed of an exotic quark Q with charge 4e/3 is excluded at 92% confidence level. Using a Bayesian approach, an upper limit on the fraction of exotic quarks p < 0.80 at 90% confidence level is obtained.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , x, 125 p.
Trita-FYS, ISSN 0280-316X ; 2006:69
National Category
Physical Sciences
URN: urn:nbn:se:kth:diva-4188ISBN: 91-7178-493-4OAI: diva2:11137
2006-11-24, Sal FB54, AlbaNova univ centrum, Roslagstullsbacken 21, Stockholm, 14:00
QC 20101116Available from: 2006-11-27 Created: 2006-11-27 Last updated: 2010-11-16Bibliographically approved

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