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Title: Measurement of z boson transverse momentum in proton - anti-proton collisions at √s = 1.96 TeV

Abstract

This dissertation describes a measurement of the shape of the boson transverse momentum distribution in p$$\bar{p}$$ → Z/γ* → e +e - + X events at a center-of-mass energy of 1.96 TeV. The measurement is made for events with electron-positron mass between 70 < M ee < 110 GeV/c 2 and uses 976 pb -1 of data collected at the Fermilab Tevatron collider with the D0 detector. The shape is measured both for the inclusive sample and for the subset of events containing a boson with large rapidity. The large-rapidity distribution shows better agreement with theory when the calculation is done using traditional Collins-Soper-Sterman resummation than when using a recent resummed form factor with modifications in the small-x region.

Authors:
 [1]
  1. Univ. of Maryland, College Park, MD (United States)
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
920110
Report Number(s):
FERMILAB-THESIS-2007-37
TRN: US0806577
DOE Contract Number:
AC02-07CH11359
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; BOSONS; DISTRIBUTION; FERMILAB TEVATRON; FORM FACTORS; MODIFICATIONS; PARTICLE RAPIDITY; PROTONS; SHAPE; TRANSVERSE MOMENTUM; Experiment-HEP

Citation Formats

Wang, Lei. Measurement of z boson transverse momentum in proton - anti-proton collisions at √s = 1.96 TeV. United States: N. p., 2007. Web. doi:10.2172/920110.
Wang, Lei. Measurement of z boson transverse momentum in proton - anti-proton collisions at √s = 1.96 TeV. United States. doi:10.2172/920110.
Wang, Lei. Mon . "Measurement of z boson transverse momentum in proton - anti-proton collisions at √s = 1.96 TeV". United States. doi:10.2172/920110. https://www.osti.gov/servlets/purl/920110.
@article{osti_920110,
title = {Measurement of z boson transverse momentum in proton - anti-proton collisions at √s = 1.96 TeV},
author = {Wang, Lei},
abstractNote = {This dissertation describes a measurement of the shape of the boson transverse momentum distribution in p$\bar{p}$ → Z/γ* → e+e- + X events at a center-of-mass energy of 1.96 TeV. The measurement is made for events with electron-positron mass between 70 < Mee < 110 GeV/c2 and uses 976 pb-1 of data collected at the Fermilab Tevatron collider with the D0 detector. The shape is measured both for the inclusive sample and for the subset of events containing a boson with large rapidity. The large-rapidity distribution shows better agreement with theory when the calculation is done using traditional Collins-Soper-Sterman resummation than when using a recent resummed form factor with modifications in the small-x region.},
doi = {10.2172/920110},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Thesis/Dissertation:
Other availability
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  • In 1961 Sheldon Lee Glashow, while working on electroweak unification gauge theory, developed a model in which he introduced a massive neutral intermediate vector boson, call Z [1], [2], [3]. By 1967 Steven Weinberg and Abdus Salam had independently solved the theoretical problems with this model and developed their own self-consistent theory. In this thesis the Z gauge boson production rate at CDF as a function of the Z transverse momentum is studied in the dimuon channel.
  • 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
  • We present a measurement of the top quark mass and of the top-antitop ( tf) pair production cross section and a search for the Standard Model Higgs boson with CDF II Detector in pp collisions atmore » $$\sqrt{s}$$ = 1.96 TeV. The integrated luminosity of 2.9 $$fb^{-1}$$ is used for top-antitop pair production cross section and top quark mass measurement. We adopt a neural-network algorithm to select candidate events from six or more jets. At least one of these jets should be required to be b jet, as identified by the reconstruction of a secondary vertex inside the jet. The mass measurement is based on a likelihood fit incorporating reconstructed mass distributions representative of signal and background, where the absolute jet energy scale (JES) is measured simultaneously with the top quark mass. The measurement yields a value of 174.8 ± 2.4 (stat + JES) $$^{+1.2}_{-1.0}$$ (syst) GeV/$c^2$ , where the uncertainty from the absolute jet energy scale is evaluated together with the statistical uncertainty. The procedure also measures the amount of signal from which we derive a cross section, $$\sigma_{t\bar{t}}$$ = 7.2 ± 0.5 (stat) ±1.0 (syst) ± 0.4 (lum) $pb$, for the measured values of top quark mass and JES. Top quark mass and W boson mass constrain the mass of the Standard Model Higgs boson, indirectly. This prediction implies MH = 89 $$^{+35}_{-26}$$GeV/$c^2$ (68% confidence level) as of July 2010. Therefore, we concentrate on the Standard Model Higgs mass search region with $$\le$$ 135 GeV / $c^2$ . Then, we search for the Standard Model Higgs boson associated with vector boson using the decay modes consisting of leptons only: Signal processes are $$WH \to \ell \nu + \tau\tau$$ and $$ZH \to l l + \tau \tau$$. We simply select 3 or 4 lepton including hadronic T to pick candidate events out. To improve search sensitivity, we adopt Support Vector Machine to discriminate signals from backgrounds. Using about 6.2 $$fb^{-1}$$ data, there was no clear discrepancy between data and our background estimation. Therefore, we extract cross section upper limit of the Standard Model Higgs production at 95 % confidence level. The observed upper limit on assumption of $$M_H$$ = 115 GeV/$c^2$ is 25.1 x $$\sigma^{SM}$$ at 95% confidence level while the expectation is 17.3 x $$\sigma ^{SM}$$ at 95%.« less
  • High-precision measurements are made of Z boson production in proton-antiproton collisions at √s = 1.96 TeV recorded by the Collider Detector at Fermilab, using the electron decay channel. The cross-section times branching ratio is measured to be σ Z · Br(Z → e +e -) = (255.7 ± 2.4 stat ± 5.2 sys ± 15.2 lum)pb in a dataset of 194 pb -1 collected between March 2002 and June 2003. This agrees well with theoretical predictions. The cross-section for W boson production in the electron channel has also been measured in the subset of this dataset of 72 pb -1more » collected up until January 2003. Using this smaller dataset the ratio of cross-sections is determined to be R ≡ σ W · Br(W → eν)/σ Z · Br(Z → ee) = 10.82 ± 0.18 stat ± 0.16 sys. Combining these results with measurements made in the muon channel gives R = 10.92 ± 0.15 stat ± 0.14 sys (e + μ channels), from which the branching ratio of the W to electrons and muons, and the total width of the W, have been extracted: Br(W → lν) = 0.1089 ± 0.0022 (l = e,μ); Γ(W) = 2078.8 ± 41.4 MeV, which are in good agreement with the Standard Model values and with other measurements. The CKM quark mixing matrix element |V cs| has been extracted: |V cs| = 0.967 ± 0.030. The rapidity distribution dσ/dy for Z → ee has also been measured over close to the full kinematic range using 194 pb -1 of data, and is found to be in good agreement with the NNLO prediction.« less
  • This thesis is organized as the following: * Chapter 1 gives a brief introduction to the theoretical understanding of Z production.* Chapter 2 brie y discusses the modern technological wonder: the Fermilab Tevatron, a pp collider that made this thesis possible. * In chapter 3, the D0 detector and its relevant sub-components for this analysis are outlined. * In chapter 4, the data sample for this analysis and its quality are described. * The fast Monte Carlo simulation, a critical part of this thesis, is described in chapter 5. * In chapter 6, the measurement of themore » $$\frac{dN(Z \to e^+ e^-)}{dP_{T}}$$ is discussed.* In chapter 7, the measurement of the $$\frac{d\sigma(p\bar{p} \to Z + X)}{dP_{T}}$$ is presented. * The conclusion and discussion are given in Chapter 8.« less