Download or read book Measurement of the Top Quark Mass Using Charged Particles in Pp Collisions at u221A s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A novel technique for measuring the mass of the top quark that uses only the kinematic properties of its charged decay products is presented. Top quark pair events with final states with one or two charged leptons and hadronic jets are selected from the data set of 8 TeV proton-proton collisions, corresponding to an integrated luminosity of 19.7 fb-1. By reconstructing secondary vertices inside the selected jets and computing the invariant mass of the system formed by the secondary vertex and an isolated lepton, an observable is constructed that is sensitive to the top quark mass that is expected to be robust against the energy scale of hadronic jets. The main theoretical systematic uncertainties, concerning the modeling of the fragmentation and hadronization of b quarks and the reconstruction of secondary vertices from the decays of b hadrons, are studied. A top quark mass of 173.68±0.20(stat)-0.97+1.58(syst) GeV is measured. Furthermore, the overall systematic uncertainty is dominated by the uncertainty in the b quark fragmentation and the modeling of kinematic properties of the top quark.
Download or read book A Precision Measurement of the Top Quark Mass written by Kevin Matthew Black and published by . This book was released on 2005 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Measurement of the Top Quark Mass in the Dilepton Final State Using the Matrix Element Method written by Alexander Grohsjean and published by Springer Science & Business Media. This book was released on 2010-10-01 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Measurements of the Top quark Mass Using Charged Particle Tracking written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present three measurements of the top-quark mass in the lepton plus jets channel with approximately 1.9 fb−1 of integrated luminosity collected with the CDF II detector using quantities with minimal dependence on the jet energy scale. One measurement exploits the transverse decay length of b-tagged jets to determine a top-quark mass of 166.9{sub -8.5}{sup +9.5} (stat) ± 2.9 (syst) GeV/c2, and another the transverse momentum of electrons and muons from W-boson decays to determine a top-quark mass of 173.5{sub -8.9}{sup +8.8} (stat) ± 3.8 (syst) GeV/c2. These quantities are combined in a third, simultaneous mass measurement to determine a top-quark mass of 170.7 ± 6.3 (stat) ± 2.6 (syst) GeV/c2.
Download or read book Measurement of the Mass of the Top Quark in Decays with a J psi Meson in Pp Collisions at 8 TeV written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A first measurement is presented of the top quark mass using the decay channel $ \mathrm{ t } \to (\mathrm{ W } \to\ell\nu)$, $(\mathrm{ b } \to \mathrm{ J } / \psi + \mathrm{X} \to \mu \mu + \mathrm{X}) $, in events selected in proton-proton collisions and recorded with the CMS detector at the LHC at a center-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of 19.7 fb$^{-1}$, with 666 $\mathrm{ t \bar{t} }$ and single top quark candidate events containing a reconstructed $\mathrm{ J } / \psi$ candidate decaying into an oppositely-charged muon pair. The mass of the ($\mathrm{ J } / \psi+\ell$) system, where $\ell$ is an electron or a muon from W boson decay, is used to extract a top quark mass of 173.5 $\pm$ 3.0 (stat) $\pm$ 0.9 (syst) GeV.
Download or read book Measurement of the Top quark Mass in All jets t bar t Events in Pp Collisions at sqrt s written by and published by . This book was released on 2013 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mass of the top quark is measured using a sample of $t\bar{t}$ candidate events with at least six jets in the final state. The sample is selected from data collected with the CMS detector in pp collisions at $\sqrt{s}$ = 7 TeV in 2011 and corresponds to an integrated luminosity of 3.54 inverse femtobarns. The mass is reconstructed for each event employing a kinematic fit of the jets to a $t\bar{t}$ hypothesis. The top-quark mass is measured to be 173.49 $\pm$ 0.69 (stat.) $\pm$ 1.21 (syst.) GeV. A combination with previously published measurements in other decay modes by CMS yields a mass of 173.54 $\pm$ 0.33 (stat.) $\pm$ 0.96 (syst.) GeV.
Download or read book Top Quark Pair Production Cross Sections and Calibration of the Top Quark Monte Carlo Mass written by Jan Kieseler and published by Springer. This book was released on 2016-06-15 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Measurement of the Mass Difference Between Top Quark and Antiquark in Pp Collisions at Sqrt s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The invariance of the standard model (SM) under the CPT transformation predicts equality of particle and antiparticle masses. This prediction is tested by measuring the mass difference between the top quark and antiquark (Delta m[t] = m[t] - m[t-bar]) that are produced in pp collisions at a center-of-mass energy of 8 TeV, using events with a muon or an electron and at least four jets in the final state. The analysis is based on data corresponding to an integrated luminosity of 19.6 inverse-femtobarns collected by the CMS experiment at the LHC, and yields a value of Delta m[t] = -0.15 +/- 0.19 (stat) +/- 0.09 (syst) GeV, which is consistent with the SM expectation. This result is significantly more precise than previously reported measurements.
Download or read book Measurement of the Charge Asymmetry in Top Quark Pair Production in Pp Collisions at sqrt s written by and published by . This book was released on 2015 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: The charge asymmetry in the production of top quark and antiquark pairs is measured in proton-proton collisions at a center-of-mass energy of 8 TeV. The data, corresponding to an integrated luminosity of 19.6 fb -1 were collected by the CMS experiment at the LHC. Events with a single isolated electron or muon, and four or more jets, at least one of which is likely to have originated from hadronization of a bottom quark, are selected. A template technique is used to measure the asymmetry in the distribution of differences in the top quark and antiquark absolute rapidities. The measured asymmetry is Ayc= [0.33_0.26 (stat)_0.33 (syst)]%, which is the most precise result to date. The results are compared to calculations based on the standard model and on several beyond-the-standard-model scenarios.
Download or read book Measurement of the Top Quark Mass Using Single Top Quark Events in Proton proton Collisions at sqrt s written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A measurement of the top quark mass is reported in events containing a single top quark produced via the electroweak t channel. The analysis is performed using data from proton-proton collisions collected with the CMS detector at the LHC at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 inverse femtobarns. The top quark is reconstructed from its decay to a W boson and a b quark, with the W boson decaying leptonically to a muon and a neutrino. The specific topology and kinematic properties of single top quark events in the t channel are used to enhance the purity of the sample, suppressing the contribution from top quark pair production. A fit to the invariant mass distribution of reconstructed top quark candidates yields a value of the top quark mass of 172.95 +/- 0.77 (stat) +0.97/-0.93 (syst) GeV. This result is in agreement with the current world average, and represents the first measurement of the top quark mass in event topologies not dominated by top quark pair production.
Download or read book First Measurement of the Running of the Top Quark Mass written by Matteo M. Defranchis and published by Springer Nature. This book was released on 2022-01-03 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, the first measurement of the running of the top quark mass is presented. This is a fundamental quantum effect that had never been studied before. Any deviation from the expected behaviour can be interpreted as a hint of the presence of physics beyond the Standard Model. All relevant aspects of the analysis are extensively described and documented. This thesis also describes a simultaneous measurement of the inclusive top quark-antiquark production cross section and the top quark mass in the simulation. The measured cross section is also used to precisely determine the values of the top quark mass and the strong coupling constant by comparing to state-of-the-art theoretical predictions. All the theoretical and experimental aspects relevant to the results presented in this thesis are discussed in the initial chapters in a concise but complete way, which makes the material accessible to a wider audience.
Download or read book Measurement of the T tbar Production Cross Section in P pbar Collisions at u221A s written by and published by . This book was released on 2006 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is the most massive fundamental particle observed so far, and the study of its properties is interesting for several reasons ranging from its possible special role in electroweak symmetry breaking to its sensitivity to physics beyond the standard model (SM). In particular, the measurement of the top quark pair production cross section ?t$ar{t}$ is of interest as a test of QCD predictions. Recent QCD calculations done with perturbation theory to next-to-leading order predict ?t$ar{t}$ with an uncertainty of less than 15%, which motivate measurements of comparable precision. In this thesis, the author reports a measurement of the cross section for pair production of top quarks in the lepton+jets channel in 318 pb-1 of p$ar{p}$ collision data at √s = 1.96 TeV. The data were recorded between March 2002 and September 2004, during Run II of the Tevatron, by the CDF II detector, a general purpose detector which combines charged particle trackers, sampling calorimeters, and muon detectors. processes in which a W boson is produced in association with several jets with large transverse momentum can be misidentified at t$ar{t}$, since they have the same signature. In order to separate the t$ar{t}$ events from this background, they develop a method to tag b-jets based on tracking information from the silicon detector. The main event selection requires at least one tight (more restrictive) b tag in the event. As a cross check, they also measure the cross section using events with a loose (less restrictive) b tag and events which have at least two tight or at least two loose b tags. Background contributions from heavy flavor production processes, such as Wb$ar{b}$, Wc$ar{c}$ or Wc, misidentified W bosons, electroweak processes, single top production, and mistagged jets are estimated using a combination of Monte Carlo calculations and independent measurements in control data samples. An excess over background in the number of events that contain a lepton, missing energy and three or more jets with at least one b-tag is assumed to be a signal of t$ar{t}$ production and is used to measure the production cross section ?t$ar{t}$.
Download or read book Measurement of the Top Quark Mass in the All Hadronic Channel at the Tevatron written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 pp 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 tt 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.
Download or read book Measurement of the Top Quark Mass from B tagged Events in the Lepton Plus Jets Channel in Pp Collisions at square Root of S written by Nathan Robert-Claire Eddy and published by . This book was released on 1999 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of the t bar t Production Cross Section in Pp Collisions at sqrt s written by and published by . This book was released on 2014 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top-quark pair production cross section is measured in final states with one electron or muon and one hadronically decaying [tau] lepton from the process $t\bar{t}$ to (l[nu]l) ([tau][nu][tau]) $b\bar{b}$, where l = e, [mu]. The data sample corresponds to an integrated luminosity of 19.6 fb-1 collected with the CMS detector in proton-proton collisions at $\sqrt{s}$ =8 TeV. The measured cross section [sigma]$t\bar{t}$ = 257 ± 3 (stat) ± 24 (syst) ± 7 (lumi) pb, assuming a top-quark mass of 172.5 GeV, is consistent with the standard model prediction.
Download or read book Top Quark Pair Production written by Anna Christine Henrichs and published by Springer. This book was released on 2016-08-23 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Measurement of the Top Quark Pair Production Cross Section in P Anti p Collisions at u221A s written by and published by . This book was released on 2006 with total page 377 pages. Available in PDF, EPUB and Kindle. Book excerpt: The subject of this thesis is the measurement of the rate at which a top-antitop quark pair is produced in pp collisions at a center of mass energy of ps = 1:96 TeV. The data are collected with the D detector, a multi-purpose detector operating at the Fermilab Tevatron collider during Run II. A measurement of the top quark pair (t$\bar{t}$) production cross section ( ?t$\bar{t}$) in p$\bar{p}$ collisions at a center of mass energy of 1.96 TeV is presented. The measurement is based on data recorded by the D0 Detector at the Fermilab Tevatron Collider, and preselected in the e+jets (366 pb-1) and ?+jets (363 pb-1) channels. The cross section is extracted by applying a lifetime-tagging technique to the data, and yields ?t$\bar{t}$ = 6.96$+1.07\atop{-0.98}$(stat + syst) ± 0.45(lumi) pb; for a top quark mass mt =175 GeV, in good agreement with the Standard Model prediction.
