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Title: Measurement of the top quark pair production cross section with 1.12 $$fb^{-1}$$ of $$p\overline{p}$$ collisions at $$\sqrt{s}$$ = 1.96 TeV

Abstract

We present a measurement of the top quark pair production cross section in e+jets and µ+jets events recorded with the CDF II detector. The data correspond to 1.12 fb -1 of pp collisions with center-of-mass energy 1.96 TeV taken during Run 2 of the Fermilab Tevatron. We identify tt candidate events by requiring at least one secondary vertex b-tag, and we measure a production cross section of 8.2 ±0.5 (stat) ±0.8 (syst) ±0.5 (lum) pb, the most precise single measurement of σtt to date. As a check, we also measure σtt in events with multiple b-tagged jets using a higher-efficiency tagging algorithm, and there we measure 8.8 +0.8 -0.7 (stat) ±1.2 (syst) ±0.5 (lum) pb, also the most precise single measurement with this signature. Both results assume a top quark mass of 175 GeV/c 2 , for which the theoretical expectation is 6.7 +0.7 -0.9 pb; the measured excess is of the order 1σ, and becomes less significant at the current world average top mass of 171 GeV/c 2 .

Authors:
 [1]
  1. Harvard Univ., Cambridge, MA (United States)
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1415816
Report Number(s):
FERMILAB-THESIS-2007-82; AAT-3285547; PROQUEST-1421625931
776426
DOE Contract Number:
AC02-07CH11359
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Sherman, Daniel Joseph. Measurement of the top quark pair production cross section with 1.12 $fb^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}$ = 1.96 TeV. United States: N. p., 2007. Web. doi:10.2172/1415816.
Sherman, Daniel Joseph. Measurement of the top quark pair production cross section with 1.12 $fb^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}$ = 1.96 TeV. United States. doi:10.2172/1415816.
Sherman, Daniel Joseph. Fri . "Measurement of the top quark pair production cross section with 1.12 $fb^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}$ = 1.96 TeV". United States. doi:10.2172/1415816. https://www.osti.gov/servlets/purl/1415816.
@article{osti_1415816,
title = {Measurement of the top quark pair production cross section with 1.12 $fb^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}$ = 1.96 TeV},
author = {Sherman, Daniel Joseph},
abstractNote = {We present a measurement of the top quark pair production cross section in e+jets and µ+jets events recorded with the CDF II detector. The data correspond to 1.12 fb-1 of pp collisions with center-of-mass energy 1.96 TeV taken during Run 2 of the Fermilab Tevatron. We identify tt candidate events by requiring at least one secondary vertex b-tag, and we measure a production cross section of 8.2 ±0.5 (stat) ±0.8 (syst) ±0.5 (lum) pb, the most precise single measurement of σtt to date. As a check, we also measure σtt in events with multiple b-tagged jets using a higher-efficiency tagging algorithm, and there we measure 8.8 +0.8 -0.7 (stat) ±1.2 (syst) ±0.5 (lum) pb, also the most precise single measurement with this signature. Both results assume a top quark mass of 175 GeV/c 2 , for which the theoretical expectation is 6.7 +0.7 -0.9 pb; the measured excess is of the order 1σ, and becomes less significant at the current world average top mass of 171 GeV/c 2 .},
doi = {10.2172/1415816},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Jun 01 00:00:00 EDT 2007},
month = {Fri Jun 01 00:00:00 EDT 2007}
}

Thesis/Dissertation:
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  • This dissertation presents a new measurement of pmore » $$\bar{p}$$ → t$$\bar{t}$$X production at √s = 1.96 TeV using 974.2 pb -1of data collected with the D0 detector between 2002 and 2006. We focus on the final state where the W boson from one of the top quarks decays into a τ lepton and its associated neutrino, while the other W boson decays into a quark-antiquark pair. We aim to select those events in which the τ lepton subsequently decays hadronically, meaning to one or three charged hadrons, zero or more neutral hadrons and a tau neutrino (the charge conjugate processes are implied in all of the above). The observable signature thus consists of a narrow calorimeter shower with associated track(s) characteristic of a hadronic tau decay, four or more jets, of which two are initiated by b quarks accompanying the W's in the top quark decays, and a large net missing momentum in the transverse plane due to the energetic neutrino-antineutrino pair that leave no trace in the detector media. The preliminary result for the measured cross section is: σ(t$$\bar{t}$$) = 6.9 -1.2 +1.2(stat) -0.7 +0.8(syst) ± 0.4 (lumi) pb. This indicates that our finding is consistent with the Standard Model prediction.« less
  • Particle physics is the branch of science that aims to explain the behavior of the most basic building blocks of the universe: elementary particles. During the 20th century, physicists made great achievements in this field. This chapter first gives an overview of modern particle physics theory, then presents the basis of the top quark physics.
  • The subject of this thesis is the measurement of the rate at which a top-antitop quark pair is produced in pp collisions at a center of mass energy of ps = 1:96 TeV. The data are collected with the D detector, a multi-purpose detector operating at the Fermilab Tevatron collider during Run II. A measurement of the top quark pair (tmore » $$\bar{t}$$) production cross section ( σ t$$\bar{t}$$) in p$$\bar{p}$$ collisions at a center of mass energy of 1.96 TeV is presented. The measurement is based on data recorded by the D0 Detector at the Fermilab Tevatron Collider, and preselected in the e+jets (366 pb -1) and μ+jets (363 pb -1) channels. The cross section is extracted by applying a lifetime-tagging technique to the data, and yields σ t$$\bar{t}$$ = 6.96$$+1.07\atop{-0.98}$$(stat + syst) ± 0.45(lumi) pb; for a top quark mass m t =175 GeV, in good agreement with the Standard Model prediction.« less
  • Two analyses are performed with the large samples of dielectron and dimuon events collected by the D0 experiment at the Fermilab Tevatronmore » $$p\bar{p}$$ collider. The dilepton transverse momentum ($$p_T$$) distribution in $$Z/\gamma^* → \ell^+\ell^-$$ production is a powerful probe of Quantum chromodynamics. Until now, this distribution has been measured with limited precision. An alternative variable, $$\phi^*_\eta$$, is proposed due to its relatively low susceptibility to detector effects. The $$\phi^*_\eta$$, distribution of events with $$Z/\gamma^* → \ell^+\ell^-$$ invariant masses between 70 and 110 GeV, is measured in three bins of dilepton rapidity. This measurement, with 7.3 fb$$^{-1}$$ of data, is significantly more precise than previous measurements of the $$p_T$$ distribution. A state-of-the-art QCD Monte Carlo program is in modest agreement with the data. Using 8.6 fb$$^{-1}$$ of data, the $$ZZ/\gamma^* → \nu\bar{\nu}\ell^+\ell^-$$ and $$WZ/\gamma^* → \ell\nu\ell^+\ell^-$$ processes are studied, yielding production cross sections of, $$\sigma(p\bar{p} \rightarrow ZZ/\gamma^*)$$ = 1.64 $$\pm$$ 0.46 p b and $$\sigma(p\bar{p} \rightarrow WZ/\gamma^*)$$ = 4.46 $$\pm$$ 0.64 pb, for $$Z/\gamma^* → \ell^+\ell^-$$ invariant masses between 60 and 130 GeV. These are in agreement with Standard Model predictions.« less