Measurement of the t-tbar production cross section in p-pbar collisions at √s = 1.96 TeV using lepton+jets events in the CDF detector at Fermilab

Thesis/Dissertation · Fri Dec 01 00:00:00 EST 2006

DOI:https://doi.org/10.2172/911833· OSTI ID:911833

Palencia, Enrique ^[1]

---

1. Univ. of Cantabria (Spain)

The top quark is the most massive fundamental particle observed so far, and the study of its properties is interesting for several reasons ranging from its possible special role in electroweak symmetry breaking to its sensitivity to physics beyond the standard model (SM). In particular, the measurement of the top quark pair production cross section σ_t$$\bar{t}$$ is of interest as a test of QCD predictions. Recent QCD calculations done with perturbation theory to next-to-leading order predict σ_t$$\bar{t}$$ with an uncertainty of less than 15%, which motivate measurements of comparable precision. In this thesis, the author reports a measurement of the cross section for pair production of top quarks in the lepton+jets channel in 318 pb^-1 of p$$\bar{p}$$ collision data at √s = 1.96 TeV. The data were recorded between March 2002 and September 2004, during Run II of the Tevatron, by the CDF II detector, a general purpose detector which combines charged particle trackers, sampling calorimeters, and muon detectors. processes in which a W boson is produced in association with several jets with large transverse momentum can be misidentified at t$$\bar{t}$$, since they have the same signature. In order to separate the t$$\bar{t}$$ events from this background, they develop a method to tag b-jets based on tracking information from the silicon detector. The main event selection requires at least one tight (more restrictive) b tag in the event. As a cross check, they also measure the cross section using events with a loose (less restrictive) b tag and events which have at least two tight or at least two loose b tags. Background contributions from heavy flavor production processes, such as Wb$$\bar{b}$$, Wc$$\bar{c}$$ or Wc, misidentified W bosons, electroweak processes, single top production, and mistagged jets are estimated using a combination of Monte Carlo calculations and independent measurements in control data samples. An excess over background in the number of events that contain a lepton, missing energy and three or more jets with at least one b-tag is assumed to be a signal of t$$\bar{t}$$ production and is used to measure the production cross section σ_t$$\bar{t}$$.

• Research Organization: Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-07CH11359
• OSTI ID: 911833
• Report Number(s): FERMILAB-THESIS-2006-50; TRN: US0800163
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ACCURACY
CALORIMETERS
CHARGED PARTICLES
CROSS SECTIONS
ELEMENTARY PARTICLES
FERMILAB COLLIDER DETECTOR
FERMILAB TEVATRON
INTERMEDIATE BOSONS
MUONS
PAIR PRODUCTION
PERTURBATION THEORY
PHYSICS
QUANTUM CHROMODYNAMICS
SENSITIVITY
SILICON
STANDARD MODEL
SYMMETRY BREAKING
T QUARKS
TRANSVERSE MOMENTUM
Experiment-HEP