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Title: Measurement of the top quark mass in the dilepton channel using the neutrino weighting algorithm at CDF II

Abstract

We measure the top quark mass using approximately 359 pb-1 of data from p$$\bar{p}$$ collisions at √s =1.96 GeV at CDF Run II. We select t$$\bar{t}$$ candidates that are consistent with two W bosons decaying to a charged lepton and a neutrino following t$$\bar{t}$$ → W +W -b$$\bar{b}$$ → l +l -v$$\bar{v}$$b$$\bar{b}$$.

Authors:
 [1]
  1. Univ. of Toronto, ON (Canada)
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:
1369282
Report Number(s):
FERMILAB-THESIS-2006-62; UMI-NR-15924
740123
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

Sabik, Simon. Measurement of the top quark mass in the dilepton channel using the neutrino weighting algorithm at CDF II. United States: N. p., 2006. Web. doi:10.2172/1369282.
Sabik, Simon. Measurement of the top quark mass in the dilepton channel using the neutrino weighting algorithm at CDF II. United States. doi:10.2172/1369282.
Sabik, Simon. Sun . "Measurement of the top quark mass in the dilepton channel using the neutrino weighting algorithm at CDF II". United States. doi:10.2172/1369282. https://www.osti.gov/servlets/purl/1369282.
@article{osti_1369282,
title = {Measurement of the top quark mass in the dilepton channel using the neutrino weighting algorithm at CDF II},
author = {Sabik, Simon},
abstractNote = {We measure the top quark mass using approximately 359 pb-1 of data from p$\bar{p}$ collisions at √s =1.96 GeV at CDF Run II. We select t$\bar{t}$ candidates that are consistent with two W bosons decaying to a charged lepton and a neutrino following t$\bar{t}$ → W+W-b$\bar{b}$ → l+l-v$\bar{v}$b$\bar{b}$.},
doi = {10.2172/1369282},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

Thesis/Dissertation:
Other availability
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  • Elementary particle physics raises questions that are several thousand years old. What are the fundamental components of matter and how do they interact? These questions are linked to the question of what happened in the very first moments after the creation of the universe. Modern physics systematically tests nature to find answers to these and other fundamental questions. Precise theories are developed that describe various phenomena and at the same time are reduced to a few basic principals of nature. Simplification and reduction have always been guiding concepts of physics. The interplay between experimental data and theoretical descriptions led tomore » the Standard Model of elementary particle physics. It summarizes the laws of nature and is one of most precise descriptions of nature achieved by mankind. Despite the great success of the Standard Model it is not the ultimate theory of everything. Models beyond the Standard Model try to unify all interactions in one grand unified theory. The number of free parameters is attempted to be reduced. Gravity is attempted to be incorporated. Extensions to the Standard Model like supersymmetry address the so-called hierarchy problem. Precision measurements are the key for searches of new particles and new physics. A powerful tool of experimental particle physics are particle accelerators. They provide tests of the Standard Model at smallest scales. New particles are produced and their properties are investigated. In 1995 the heaviest known elementary particle, called top quark, has been discovered at Fermilab. It differs from all other lighter quarks due to the high mass and very short lifetime. This makes the top quark special and an interesting object to be studied. A rich program of top physics at Fermilab investigates whether the top quark is really the particle as described by the Standard Model. The top quark mass is a free parameter of the theory that has been measured precisely. This thesis presents a precise measurement of the top quark mass by the D0 experiment at Fermilab in the dilepton final states. The comparison of the measured top quark masses in different final states allows an important consistency check of the Standard Model. Inconsistent results would be a clear hint of a misinterpretation of the analyzed data set. With the exception of the Higgs boson, all particles predicted by the Standard Model have been found. The search for the Higgs boson is one of the main focuses in high energy physics. The theory section will discuss the close relationship between the physics of the Higgs boson and the top quark.« less
  • The top quark, the most recently discovered quark, is the most massive known fundamental fermion. Precision measurements of its mass, a free parameter in the Standard Model of particle physics, can be used to constrain the mass of the Higgs Boson. In addition, deviations in the mass as measured in different channels can provide possible evidence for new physics. We describe a measurement of the top quark mass in the decay channel with two charged leptons, known as the dilepton channel, using data collected by the CDF II detector from pmore » $$\bar{p}$$ collisions with √s = 1.96 TeV at the Fermilab Tevatron. The likelihood in top mass is calculated for each event by convolving the leading order matrix element describing q$$\bar{q}$$ → t$$\bar{t}$$ → bℓv $$\bar{b}$$ℓ'v ℓ' with detector resolution functions. The presence of background events in the data sample is modeled using similar calculations involving the matrix elements for major background processes. In a data sample with integrated luminosity of 1.0 fb -1, we observe 78 candidate events and measure M t = 164.5 ± 3.9(stat.) ± 3.9(syst.) GeV/c 2, the most precise measurement of the top quark mass in this channel to date.« less
  • The top quark is the heaviest fundamental particle observed to date. The mass of the top quark is a free parameter in the Standard Model (SM). A precise measurement of its mass is particularly important as it sets an indirect constraint on the mass of the Higgs boson. It is also a useful constraint on contributions from physics beyond the SM and may play a fundamental role in the electroweak symmetry breaking mechanism. I present a measurement of the top quark mass in the dilepton channel using the Neutrino Weighting Method. The data sample corresponds to an integrated luminosity of 4.3 fb -1 of pmore » $$\bar{p}$$ collisions at Tevatron with √s = 1.96 TeV, collected with the DØ detector. Kinematically under-constrained dilepton events are analyzed by integrating over neutrino rapidity. Weight distributions of t$$\bar{t}$$ signal and background are produced as a function of the top quark mass for different top quark mass hypotheses. The measurement is performed by constructing templates from the moments of the weight distributions and input top quark mass, followed by a subsequent likelihood t to data. The dominant systematic uncertainties from jet energy calibration is reduced by using a correction from `+jets channel. To replicate the quark avor dependence of the jet response in data, jets in the simulated events are additionally corrected. The result is combined with our preceding measurement on 1 fb -1 and yields m t = 174.0± 2.4 (stat.) ±1.4 (syst.) GeV.« less
  • 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