Observation of Top Quark Pairs in the Dilepton Decay Channel using Electrons, Muons and Taus
- Chicago U.
This thesis presents a search for top quark pair production via the process p pbar -> t tbar + X -> W+W- b bbar + X -> (l+ nu_l)(l- nubar_l) b bbar + X, where l is either e, mu, or tau. Using a sample of 109+-7 pb of ppbar collisons at sqrt{s}=1.8 TeV collected by the CDF detector at the Fermilab Tevatron we find a clear signal for ttbar production in the ee, mumu, and emu dilepton channels. We observe 9 events where we expect 3.9+-0.7 ttbar events (based on the theoretical production cross section) and 2.1+-0.4 background events. The ttbar production cross section measured from this channel is sigma_{ttbar}=8.5^{+4.1}_{-3.3}(stat)^{+1.6}_{-0.8} (syst) pb. Using a method developed in this thesis to identify hadronically decaying tau leptons we also search for etau and mutau dilepton events from t tbar production and decay. We observe 4 events and expect 2.5+-0.4 background events. In 3 of the 4 events atleast one jet is tagged as due to a b quark decay. We expect 0.28+-0.02 tagged events from background processes. Based on the 4 tau dilepton events we calculate the ttbar production cross section to be sigma_{t tbar } = 10.2^{+16.3}_{-10.2}(stat)+-1.6(syst) pb. The kinematics and topology of the candidate events are generally consistent with the expectations, with two exceptions. Five of the 14 candidate events have unusually large missing transverse energy. One emu event contains an electron with very high Et (182 GeV) and an additional high--Et (23 GeV) isolated positron. In 109 pb we expect (2.4+-0.9)x10^{-6} such ``trilepton" events from t tbar production and decay. Enjoy,Marcus
- Research Organization:
- Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1421718
- Report Number(s):
- FERMILAB-THESIS-1997-41; UMI-98-00605; CDF-ANAL-TOP-CDFR-4280; 453982
- Country of Publication:
- United States
- Language:
- English
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