<p>This thesis presents two measurements of the top quark using 230 pb-1 of data taken with the D0 detector at the Tevatron accelerator. The first measurement determines the top pair production cross section at sqrt(s)=1.96 TeV in proton-antiproton collisions. In the standard model of particle physics the top quark decays almost exclusively into a W boson and a b quark. Candidate events are selected by requiring that at least one jet in the event is tagged with the secondary vertex algorithm. The measured top pair production cross section is:</p><p>8.6 +1.6-1.5 (stat. + syst.) +- 0.6 (lumi.) pb.</p><p>The second measurement uses the observed and predicted number of events with 0, 1 and 2 b-tagged jets to estimate the ratio R:</p><p>R = B(t->Wb) / B(t->Wq)</p><p>where q stands for any down-type quark. The measured value is</p><p>R = 1.03 +0.19-0.17 (stat. + syst.)</p><p>in good agreement with the standard model prediction of R=1. The result can be used to obtain a lower limit for R:</p><p>R > 0.61 (95% C.L.).</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:su-879 |
| Date | January 2006 |
| Creators | Strandberg, Jonas |
| Publisher | Stockholm University, Department of Physics, Stockholm : Fysikum |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
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