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Title: Measurement of the Top Quark Mass in the All Hadronic Channel at the Tevatron

Abstract

This study presents a measurement of the top quark mass in the all hadronic channel of the top quark pair production mechanism, using 1 fb -1 of p$$\bar{p}$$ collisions at √s =1.96 TeV collected at the Collider Detector at Fermilab (CDF). Few novel techniques have been used in this measurement. A template technique was used to simultaneously determine the mass of the top quark and the energy scale of the jets. Two sets of distributions have been parameterized as a function of the top quark mass and jet energy scale. One set of distributions is built from the event-by-event reconstructed top masses, determined using the Standard Model matrix element for the t$$\bar{t}$$ all hadronic process. This set is sensitive to changes in the value of the top quark mass. The other set of distributions is sensitive to changes in the scale of jet energies and is built from the invariant mass of pairs of light flavor jets, providing an in situ calibration of the jet energy scale. The energy scale of the measured jets in the final state is expressed in units of its uncertainty, sigmac. The measured mass of the top quark is 171.1±3.7(stat.unc.)±2.1(syst.unc.) GeV/ c 2 and to the date represents the most precise mass measurement in the all hadronic channel and third best overall.

Authors:
 [1]
+ Show Author Affiliations
  1. Univ. of Florida, Gainesville, FL (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:
1352019
Report Number(s):
FERMILAB-THESIS-2007-102
1515457
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

Lungu, Gheorghe. Measurement of the Top Quark Mass in the All Hadronic Channel at the Tevatron. United States: N. p., 2007. Web. doi:10.2172/1352019.
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Lungu, Gheorghe. Measurement of the Top Quark Mass in the All Hadronic Channel at the Tevatron. United States. doi:10.2172/1352019.
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Lungu, Gheorghe. Mon . "Measurement of the Top Quark Mass in the All Hadronic Channel at the Tevatron". United States. doi:10.2172/1352019. https://www.osti.gov/servlets/purl/1352019.
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@article{osti_1352019,
title = {Measurement of the Top Quark Mass in the All Hadronic Channel at the Tevatron},
author = {Lungu, Gheorghe},
abstractNote = {This study presents a measurement of the top quark mass in the all hadronic channel of the top quark pair production mechanism, using 1 fb-1 of p$\bar{p}$ collisions at √s =1.96 TeV collected at the Collider Detector at Fermilab (CDF). Few novel techniques have been used in this measurement. A template technique was used to simultaneously determine the mass of the top quark and the energy scale of the jets. Two sets of distributions have been parameterized as a function of the top quark mass and jet energy scale. One set of distributions is built from the event-by-event reconstructed top masses, determined using the Standard Model matrix element for the t$\bar{t}$ all hadronic process. This set is sensitive to changes in the value of the top quark mass. The other set of distributions is sensitive to changes in the scale of jet energies and is built from the invariant mass of pairs of light flavor jets, providing an in situ calibration of the jet energy scale. The energy scale of the measured jets in the final state is expressed in units of its uncertainty, sigmac. The measured mass of the top quark is 171.1±3.7(stat.unc.)±2.1(syst.unc.) GeV/c 2 and to the date represents the most precise mass measurement in the all hadronic channel and third best overall.},
doi = {10.2172/1352019},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
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Thesis/Dissertation:
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DOI:  10.2172/1352019
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  • A measurement of the top quark mass in proton-antiproton collisions at √s = 1.96 TeV using 1040fb -1 of data collected in D detector at Fermilab is presented. This analysis focuses on the all-hadronic decay mode of the top quark and therefore only events with six or more calorimeter jets in the final state are considered.

  • We report a measurement of the top quark mass in the all-hadronic channel with the upgraded Collider Detector at Fermilab using an integrated luminosity of 1.02more » $$fb^{-1}$$ . Top quarks are produced mostly in pairs at the Tevatron Collider; they subsequently decay almost 100% of the time in a W boson and a b quark each. Final states are classified according to the decays of the W bosons. Here we study only those events in which both W's decay into quark pairs. This channel has the advantage of a large branching ratio and of being fully reconstructed. On the other hand the signal is overwhelmed by a background which surpasses it by three orders of magnitude even after the requirement of a specific trigger. A neural network is thus used to discriminate signal from background events in order to achieve a good signal over background ratio. We look for a variable which is strongly correlated with the top quark mass, and compare the corresponding distribution in the data to signal and background templates in order to measure the top quark mass. Here is an outline of the following of this work: Chapter 1 presents an introduction to the path that lead to the formalization of the Standard Model of fundamental interactions. We discuss in Chapter 2 the need for a 6th quark in the Standard Model, the phenomenology of the top quark and a summary of the current experimental knowledge of its properties, and motivate the need for a precise measurement of its mass. In Chapter 3 we describe the experimental apparatus needed to produce the top quarks, i.e. the Tevatron Collider, and the detector which collects the data analyzed in this work, CDF II. Chapter 4 describes how CDF II interprets the output from the various subdetectors and translate them into the physics objects which are needed for the measurement. In Chapter 5 we present how we overcome the problem of the huge background which overwhelms the top production by using for the first time in this channel a neural network approach to select the candidate events. Finally, in Chapter 6 we present and discuss the technique used to extract the top quark mass measurement, how we control this technique, evaluate the systematics uncertainties, and finally apply the method to the data to obtain the top quark mass measurement.« less

  • The top quark is the heaviest standard model quark. Discovered in 1995 by the two Tevatron experiments it has atypical properties. In particular its time life is so short that it decays before hadronizing, so the top quark mass could be measured with a high precision. Data collected by the DØ experiment between 2002 and 2009, which represent an integrated luminosity of 5.4 fb⁻¹, are used to measure the top quark mass by using the matrix element method in the three dilepton channels: dielectron, electron--muon and dimuon. The measured mass, 174.0 ± 1.8 (stat.) ± 2.4 (syst.) GeV, is inmore » a good agreement with other measurements and limited by the systematic uncertainties for the first time in these channels. In this thesis different approaches have been studied to improve the accuracy of this measurement: the use of b-quark jet identification in order to optimize the selection of top--anti-top events and a better determination of the main systematic uncertainties. A special attention has been paid to the Monte-Carlo simulation of muons in D0: the improved smearing procedure for the simulated muons, discussed in this thesis, will be used to increase the accuracy of the top properties measurements as well as the precision of many other D0 measurements.« less

  • We describe a measurement of the top quark mass inmore » $$t\overline{t}$$ production where the final state is 6 or more jets, which is otherwise known as the all-jets channel. The mass is extracted from 110.2 $$pb^{-1}$$ of data taken with the D0 detector at the Fermilab Tevatron (center-of-mass energy ps = 1.8 TeV) from 1993-96. The top quark mass is measured to be $$176.6^{+17.1}_{-13.4}$$ $GeV/c^2$. The corresponding cross section is estimated to be $$11.5^{+4.9}_{-4.7}$$ pb.« less

  • The top quark is the heaviest fermion observed to date. A precise measurement of its mass and W boson mass is important to indirect measurements of Higgs boson mass. Furthermore, the top quark mass, W boson mass and Higgs boson mass may test the Standard Model using the correlations between them. Here in this thesis, we present a measurement of the top quark mass in the all hadronic final state using the template method. This final state has the advantage of being fully reconstructed in the detector and having the largest branching fraction. The measurement is performed on 4033 candidatemore » events collected using the DØ detector. The data is collected from pp collisions generated at √s =1.96 GeV by the TEVATRON accelerator, Fermi National Accelerator Laboratory, Batavia IL. This is a two dimensional measurement formulated to extract the top quark mass as well as lower the systematic uncertainty due to the jet energy scale calibration. A kinematic fitter is employed to build the templates of signal and background for various input top quark mass points and jet energy scale variations. These templates are compared to data to obtain the fitted top quark mass, jet energy scale shift and their uncertainties.« less