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Title: Measurement of Top Quark Properties and Search for the Standard Model Higgs Boson in Proton Anti-Proton Collisions at $$\sqrt{s}$$ = 1.96 TeV

Abstract

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 at $$\sqrt{s}$$ = 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%.

Authors:
 [1]
  1. Waseda Univ., Shinjuku (Japan)
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:
1353471
Report Number(s):
FERMILAB-THESIS-2011-71
1516537
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

Ebina, Koji. Measurement of Top Quark Properties and Search for the Standard Model Higgs Boson in Proton Anti-Proton Collisions at $\sqrt{s}$ = 1.96 TeV. United States: N. p., 2011. Web. doi:10.2172/1353471.
Ebina, Koji. Measurement of Top Quark Properties and Search for the Standard Model Higgs Boson in Proton Anti-Proton Collisions at $\sqrt{s}$ = 1.96 TeV. United States. doi:10.2172/1353471.
Ebina, Koji. Tue . "Measurement of Top Quark Properties and Search for the Standard Model Higgs Boson in Proton Anti-Proton Collisions at $\sqrt{s}$ = 1.96 TeV". United States. doi:10.2172/1353471. https://www.osti.gov/servlets/purl/1353471.
@article{osti_1353471,
title = {Measurement of Top Quark Properties and Search for the Standard Model Higgs Boson in Proton Anti-Proton Collisions at $\sqrt{s}$ = 1.96 TeV},
author = {Ebina, Koji},
abstractNote = {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 at $\sqrt{s}$ = 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%.},
doi = {10.2172/1353471},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2011},
month = {3}
}

Thesis/Dissertation:
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