A Precision Measurement of the Top Quark Mass

A Precision Measurement of the Top Quark Mass
Author: Kevin Matthew Black
Publisher:
Total Pages: 226
Release: 2005
Genre:
ISBN:

This dissertation describes the measurement of the top quark mass using events recorded during a {approx} 230 pb{sup -1} exposure of the D0 detector to proton-anti-proton (p{bar p}) collisions at a center of mass energy of 1.96 TeV. The Standard Model of particle physics predicts that the top quark will decay into a bottom quark and a W boson close to 100% of the time. The bottom quark will hadronize (bind with another quark) and produce a jet of hadronic particles. The W bosons can decay either into a charged lepton and a neutrino or a pair of quarks. this dissertation focuses on the top quark (t{bar t}) events in which one W decays hadronically and the other decays leptonically. Two methods of identifying t{bar t} events from the large number of events produced are used. The first is based on the unique topology of the final state particles of a heavy particle. By using the topological information of the event, the t{bar t} events can be efficiently extracted from the background. The second method relies on the identification of the remnants of the long lived bottom quarks that are expected to be produced in the decay of almost every top quark. Because the largest background processes do not contain bottom quarks, this is an extremely efficient way to select the events retaining about 60% of the t{bar t} events and removing almost 90% of the background. A kinematic fit to the top quark mass is performed on the t{bar t} candidate events using the final state particles that are seen in the detector. A likelihood technique is then used to extract the most likely value of the top quark mass, m{sub t}, and signal fraction. The result for the topological selection is m{sub t} = 169.9 {+-} 5.8(statistical){sub -7.8}{sup +8.0}(systematic) GeV while the results on the sample selected from identification of a b quark in the event is m{sub t} = 170.6 {+-} 4.2(statistical){sub -6.8}{sup +6.3}(systematic) GeV.

Precision Measurement of the Mass of the Top Quark in P $\bar{p}$ Collisions

Precision Measurement of the Mass of the Top Quark in P $\bar{p}$ Collisions
Author:
Publisher:
Total Pages: 125
Release: 2007
Genre:
ISBN:

We report a measurement of the mass of the top quark (mtop) in p$ar{p}$ collisions at a center of mass energy of 1.96 TeV. The analysis is based on p$ar{p}$→t$ar{t}$→ lepton+jets data recorded with the D0 detector at the Fermilab Tevatron Collider. Events were preselected in the e+jets (913 events/pb of data) and in the ?+jets (871 events/pb of data) channels. These were analyzed through a comparison of the matrix element for the production and decay of the t$ar{t}$ states with data, using a likelihood method and 'tagged' b quarks from the t → Wb decays.

Top Quark Pair Production

Top Quark Pair Production
Author: Anna Christine Henrichs
Publisher: Springer Science & Business Media
Total Pages: 231
Release: 2013-10-04
Genre: Science
ISBN: 3319014870

Before any kind of new physics discovery could be made at the LHC, a precise understanding and measurement of the Standard Model of particle physics' processes was necessary. The book provides an introduction to top quark production in the context of the Standard Model and presents two such precise measurements of the production of top quark pairs in proton-proton collisions at a center-of-mass energy of 7 TeV that were observed with the ATLAS Experiment at the LHC. The presented measurements focus on events with one charged lepton, missing transverse energy and jets. Using novel and advanced analysis techniques as well as a good understanding of the detector, they constitute the most precise measurements of the quantity at that time.

Precision Measurement of the Mass of the Top Quark in P Anti-p Collisions

Precision Measurement of the Mass of the Top Quark in P Anti-p Collisions
Author:
Publisher:
Total Pages: 125
Release: 2007
Genre:
ISBN:

We report a measurement of the mass of the top quark (m{sub top}) in p{bar p} collisions at a center of mass energy of 1.96 TeV. The analysis is based on p{bar p}→t{bar t}→ lepton+jets data recorded with the D0 detector at the Fermilab Tevatron Collider. Events were preselected in the e+jets (913 events/pb of data) and in the [mu]+jets (871 events/pb of data) channels. These were analyzed through a comparison of the matrix element for the production and decay of the t{bar t} states with data, using a likelihood method and 'tagged' b quarks from the t → Wb decays.

Top-Quark Pair Production Cross Sections and Calibration of the Top-Quark Monte-Carlo Mass

Top-Quark Pair Production Cross Sections and Calibration of the Top-Quark Monte-Carlo Mass
Author: Jan Kieseler
Publisher: Springer
Total Pages: 172
Release: 2016-06-15
Genre: Science
ISBN: 3319400053

This thesis presents the first experimental calibration of the top-quark Monte-Carlo mass. It also provides the top-quark mass-independent and most precise top-quark pair production cross-section measurement to date. The most precise measurements of the top-quark mass obtain the top-quark mass parameter (Monte-Carlo mass) used in simulations, which are partially based on heuristic models. Its interpretation in terms of mass parameters used in theoretical calculations, e.g. a running or a pole mass, has been a long-standing open problem with far-reaching implications beyond particle physics, even affecting conclusions on the stability of the vacuum state of our universe. In this thesis, this problem is solved experimentally in three steps using data obtained with the compact muon solenoid (CMS) detector. The most precise top-quark pair production cross-section measurements to date are performed. The Monte-Carlo mass is determined and a new method for extracting the top-quark mass from theoretical calculations is presented. Lastly, the top-quark production cross-sections are obtained – for the first time – without residual dependence on the top-quark mass, are interpreted using theoretical calculations to determine the top-quark running- and pole mass with unprecedented precision, and are fully consistently compared with the simultaneously obtained top-quark Monte-Carlo mass.

Precision Measurement of the Top-quark Mass in Lepton$+$jets Final States

Precision Measurement of the Top-quark Mass in Lepton$+$jets Final States
Author:
Publisher:
Total Pages:
Release: 2015
Genre:
ISBN:

We measure the mass of the top quark in lepton þ jets final states using the full sample of pp¯ collision data collected by the D0 experiment in Run II of the Fermilab Tevatron Collider at √s = 1.96 TeV, corresponding to 9.7 fb-1 of integrated luminosity. We also use a matrix element technique that calculates the probabilities for each event to result from tt¯ production or background. Furthermore, the overall jet energy scale is constrained in situ by the mass of the W boson. We measure mt = 174.98 ± 0.76 GeV. As a result, this constitutes the most precise single measurement of the top-quark mass.

Precision Top-Quark Mass Measurements at CDF.

Precision Top-Quark Mass Measurements at CDF.
Author:
Publisher:
Total Pages:
Release: 2012
Genre:
ISBN:

We present a precision measurement of the top-quark mass using the full sample of Tevatron √s = 1.96 TeV proton-antiproton collisions collected by the CDF II detector, corresponding to an integrated luminosity of 8.7 fb−1. Using a sample of t{bar t} candidate events decaying into the lepton+jets channel, we obtain distributions of the top-quark masses and the invariant mass of two jets from the W boson decays from data. We then compare these distributions to templates derived from signal and background samples to extract the top-quark mass and the energy scale of the calorimeter jets with in situ calibration. The likelihood fit of the templates from signal and background events to the data yields the single most-precise measurement of the top-quark mass, mtop = 172.85 ± 0.71 (stat) ± 0.85 (syst) GeV/c2.

Measurement of the Top Quark Mass in the Dilepton Final State Using the Matrix Element Method

Measurement of the Top Quark Mass in the Dilepton Final State Using the Matrix Element Method
Author: Alexander Grohsjean
Publisher: Springer Science & Business Media
Total Pages: 155
Release: 2010-10-01
Genre: Science
ISBN: 364214070X

The main pacemakers of scienti?c research are curiosity, ingenuity, and a pinch of persistence. Equipped with these characteristics a young researcher will be s- cessful in pushing scienti?c discoveries. And there is still a lot to discover and to understand. In the course of understanding the origin and structure of matter it is now known that all matter is made up of six types of quarks. Each of these carry a different mass. But neither are the particular mass values understood nor is it known why elementary particles carry mass at all. One could perhaps accept some small generic mass value for every quark, but nature has decided differently. Two quarks are extremely light, three more have a somewhat typical mass value, but one quark is extremely massive. It is the top quark, the heaviest quark and even the heaviest elementary particle that we know, carrying a mass as large as the mass of three iron nuclei. Even though there exists no explanation of why different particle types carry certain masses, the internal consistency of the currently best theory—the standard model of particle physics—yields a relation between the masses of the top quark, the so-called W boson, and the yet unobserved Higgs particle. Therefore, when one assumes validity of the model, it is even possible to take precise measurements of the top quark mass to predict the mass of the Higgs (and potentially other yet unobserved) particles.