Observation of $$t\bar{t}$$ Quark Production Using a Soft Lepton B Tag in $$p\bar{p}$$ Collisions at $$\sqrt{s}$$ = 1.8-TeV

Thesis/Dissertation · Sat Jun 01 04:00:00 EDT 1996

DOI:https://doi.org/10.2172/1372334· OSTI ID:1372334

Kestenbaum, David Samuel ^[1]

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1. Harvard Univ., Cambridge, MA (United States)

This thesis presents the results of a search for $$t\bar{t}$$ production in 110 $$pb^{-1}$$ of $$p\bar{p}$$ collisions at $$\sqrt{s}$$=l.8 TeV. The data were collected using the Collider Detector at Ferrnilab (CDF). The search identifies events consistent with the Standard Model decay ($$t\bar{t} \to W^+ bW^- \bar{b}$$). W bosons are identified by the presence of high momentum electrons or muons associated with missing energy transverse to the beam. At least three jets are required to reduce the background from W bosons produced with associated jets. Finally the presence of a b-quark is inferred by searching for a soft lepton from the semileptonic decay ($$b \to \ell \nu X$$) or the sequential decay ($$b \to c \to \ell \nu X$$). Backgrounds from falCe leptons or from real leptons occurring in generic jets are estimated from the data and account for 903 of the total background. The remaining backgrounds from Drell-Yan, $$Z \to \pi^+\pi^-$$, $$Wc, b\bar{b}$$ and Diboson production are estimated from a combination of Monte Carlo simulated events and data. Forty candidate events are identified containing 44 soft lepton tags with an expected background of 24.6 ± 3.0 tags. The probability of the background fluctuating upward to give the observed excess is 0.183. The acceptance for top quark events is calculated and the tl cross section measured to be $$\sigma_{t\bar{t}}$$ = 8.5 ± 3.4 pb. The results of this analysis are combined with the results of other searches and a kinematic fit for the top mass is performed yielding a top mass of 175.6 ± 5.7 (stat) ± 7.1 ( syst) Ge V / $c^2$ . For the measured mass the cross section is in good agreement with predictions from the Standard Model.

• 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: 1372334
• Report Number(s): FERMILAB-THESIS--1996-48; HUHEPL--22; UMI--96-31521; 428315
• Country of Publication: United States
• Language: English

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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS