Top quark pair production in proton anti-proton collisions
- Univ. of Amsterdam (Netherlands)
This thesis presents a measurement of the t$$\bar{t}$$ cross section in the all-jets channel, measured in p$$\bar{p}$$ collisions at a center of mass energy of 1.96 TeV, using data collected with the D0 detector. The dataset used for this analysis has an integrated luminosity equivalent to L = 162.5 ± 10.6 pb-1. A t$$\bar{t}$$ cross section measurement is a test of the Standard Model predictions for heavy quark production, and the first step towards measurements of the mass and other properties of the top quark. The presented measurement of the cross section for the process p$$\bar{p}$$ → t$$\bar{t}$$ uses the decay channel where both top quarks decay to quarks. The top quark first decays to a b quark and a W boson, and then, for this particular channel, the W boson decays hadronically. Hence, events with six energetic quarks are expected, which ideally leads to events with six jets. These so called all-jets events have a significantly larger branching fraction than other t$$\bar{t}$$ decay channels. The large branching fraction in the all-jets channel means that a significant sample of t$$\bar{t}$$ candidates can be extracted, which can subsequently be used for studies of top quark properties, like the top mass. The background, multijet production through Quantum Chromo Dynamics (QCD) has a cross section three to four orders of magnitude larger than expected for t$$\bar{t}$$ production. The analysis presented in this thesis uses the decay vertices of long-lived b-flavored mesons to identify the b jets. With the silicon detector installed at the start of Run 2 of the Tevatron, the D0 experiment is now able to use this method for b identification. The presence of b quarks in the event makes it possible to reduce the background to a few percent of the original sample, while only rejecting around 45% of the t$$\bar{t}$$ content in the sample.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76CH03000
- OSTI ID:
- 15017276
- Report Number(s):
- FERMILAB-THESIS-2005-02; TRN: US200606%%467
- Country of Publication:
- United States
- Language:
- English
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