Download or read book Discovery of Single Top Quark Production written by Dag Gillberg and published by Springer Science & Business Media. This book was released on 2011-01-22 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is by far the heaviest known fundamental particle with a mass nearing that of a gold atom. Because of this strikingly high mass, the top quark has several unique properties and might play an important role in electroweak symmetry breaking—the mechanism that gives all elementary particles mass. Creating top quarks requires access to very high energy collisions, and at present only the Tevatron collider at Fermilab is capable of reaching these energies. Until now, top quarks have only been observed produced in pairs via the strong interaction. At hadron colliders, it should also be possible to produce single top quarks via the electroweak interaction. Studies of single top quark production provide opportunities to measure the top quark spin, how top quarks mix with other quarks, and to look for new physics beyond the standard model. Because of these interesting properties, scientists have been looking for single top quarks for more than 15 years. This thesis presents the first discovery of single top quark production. It documents one of the flagship measurements of the D0 experiment, a collaboration of more than 600 physicists from around the world. It describes first observation of a physical process known as “single top quark production”, which had been sought for more than 10 years before its eventual discovery in 2009. Further, his thesis describes, in detail, the innovative approach Dr. Gillberg took to this analysis. Through the use of Boosted Decision Trees, a machine-learning technique, he observed the tiny single top signal within an otherwise overwhelming background. This Doctoral Thesis has been accepted by Simon Fraser University, Burnaby, BC, Canada.
Download or read book Results on Top Quark Production from written by and published by . This book was released on 1995 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: The D{O} Collaboration reports on a search for the Standard Model top quark in p{bar p} collisions at (square root)s = 1.8 TeV at the Fermilab Tevatron, with an integrated luminosity of approximately 50 pb−1. We have searched for t{bar t} production in the dilepton and single lepton channels with and without tagging of b quark jets. We observe 17 events with an expected background of 3.8 " 0.6 events. The probability for an upward, fluctuation of the background to produce the observed signal is 2 x 10−6 (equivalent to 4.6 standard deviations). The kinematic properties of the excess events are consistent with top quark decay. We conclude that we have observed the top quark and measure its mass to be 19921{sup +19}(stat.)"22 (syst.) GeV/c2 and its production cross section to be 6.4 " 2.2 pb.
Download or read book Studies of Top Quark Production at written by and published by . This book was released on 2011 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: I present recent results on top quark production in pp collisions at a center of mass energy of 1.96 TeV. The studies were performed by the D0 collaboration using approximately 5 fb−1 of data taken during Run II at the Fermilab Tevatron accelerator. The top quark is the heaviest known elementary particle and completes the quark sector of the three-generation structure of the standard model (SM). It differs from the other quarks not only by its much larger mass, but also by its lifetime which is too short to build hadronic bound states. The SM predicts that top quarks are created via two independent production mechanisms at hadron colliders. The primary mode, in which a t{bar t} pair is produced from a gtt vertex via the strong interaction, was used by the D0 and CDF collaborations to establish the existence of the top quark in 1995. The second production mode of top quarks at hadron colliders is the electroweak production of a single top quark from a Wtb vertex. The predicted cross section for single top quark production is about half that of t{bar t} pairs but the signal-to-background ratio is much worse; observation of single top quark production has therefore until recently been impeded by its low rate and difficult background environment compared to the top pair production. In the following sections I will present results for the measurement of the t{bar t} pair and the single top quark production cross section using respectively 5.3 fb−1 and 5.4 fb−1 of data taken by the D0 experiment.
Download or read book Review of Top Quark Physics Results written by and published by . This book was released on 2007 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: As the heaviest known fundamental particle, the top quark has taken a central role in the study of fundamental interactions. Production of top quarks in pairs provides an important probe of strong interactions. The top quark mass is a key fundamental parameter which places a valuable constraint on the Higgs boson mass and electroweak symmetry breaking. Observations of the relative rates and kinematics of top quark final states constrain potential new physics. In many cases, the tests available with study of the top quark are both critical and unique. Large increases in data samples from the Fermilab Tevatron have been coupled with major improvements in experimental techniques to produce many new precision measurements of the top quark. The first direct evidence for electroweak production of top quarks has been obtained, with a resulting direct determination of V{sub tb}. Several of the properties of the top quark have been measured. Progress has also been made in obtaining improved limits on potential anomalous production and decay mechanisms. This review presents an overview of recent theoretical and experimental developments in this field. We also provide a brief discussion of the implications for further efforts.
Download or read book Physics at the Large Hadron Collider written by Amitava Datta and published by Springer Science & Business Media. This book was released on 2010-05-30 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: In an epoch when particle physics is awaiting a major step forward, the Large Hydron Collider (LHC) at CERN, Geneva will soon be operational. It will collide a beam of high energy protons with another similar beam circulation in the same 27 km tunnel but in the opposite direction, resulting in the production of many elementary particles some never created in the laboratory before. It is widely expected that the LHC will discover the Higgs boson, the particle which supposedly lends masses to all other fundamental particles. In addition, the question as to whether there is some new law of physics at such high energy is likely to be answered through this experiment. The present volume contains a collection of articles written by international experts, both theoreticians and experimentalists, from India and abroad, which aims to acquaint a non-specialist with some basic issues related to the LHC. At the same time, it is expected to be a useful, rudimentary companion of introductory exposition and technical expertise alike, and it is hoped to become unique in its kind. The fact that there is substantial Indian involvement in the entire LHC endeavour, at all levels including fabrication, physics analysis procedures as well as theoretical studies, is also amply brought out in the collection.
Download or read book Recent Results of Top Quark Physics from the Tevatron written by and published by . This book was released on 2015 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Twenty years after its discovery in 1995 by the CDF and D0 collaborations at the Tevatron proton-antiproton collider at Fermilab, the top quark still undergoes intensive studies at the Tevatron and the LHC at CERN. In this article, recent top quark physics results from CDF and D0 are reported. In particular, measurements of single top quark and double top quark production, the $t\bar{t}$ forward-backward asymmetry and the top quark mass are discussed.
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 Recent Top Quark Production Results from the Tevatron written by and published by . This book was released on 2015 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Top Quark Results from written by H. B. Greenlee and published by . This book was released on 2005 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this talk I will present recent preliminary results from the D0 experiment from Tevatron Run II (p{bar p} collisions at {radical}s = 1.96 TeV). The results presented in this talk include top quark pair production cross section, top quark mass, and upper limits on single top quark production.
Download or read book The Evidence for the Top Quark written by Kent W. Staley and published by Cambridge University Press. This book was released on 2004-04-05 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Evidence for the Top Quark offers both a historical and philosophical perspective on an important recent discovery in particle physics: the first evidence for the elementary particle known as the top quark. Drawing on published reports, oral histories, and internal documents from the large collaboration that performed the experiment, Kent Staley explores in detail the controversies and politics that surrounded this major scientific result.At the same time the book seeks to defend an objective theory of scientific evidence based on error probabilities.
Download or read book Higher Order QCD Corrections to Single Top Quark Production written by Mohammad Assadsolimani and published by disserta Verlag. This book was released on 2014-08 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is known that the LHC has a considerable discovery potential because of its large centre-of-mass energy (vs =14 TeV) and the high design luminosity. In addition, the two experiments ATLAS and CMS perform precision measurements for numerous models in physics. The increasing experimental precision demands an even higher level of accuracy on the theoretical side. For a more precise prediction of outcomes, one has to consider the corrections obtained typically from Quantum Chromodynamics (QCD). The calculation of these corrections in the high energy regime is described by perturbation theory. In the present study, multi-loop calculations in QCD, including in particular two-loop corrections for single top quark production, are considered. There are several phenomenological motivations to study single top quark production: Firstly, the process is sensitive to the electroweak Wtb-vertex; moreover, non-standard couplings can hint at physics beyond the Standard Model. Secondly, the t-channel cross section measurement provides information on the b-quark Parton Distribution Functions (PDF). Finally, single top quark production enables us to directly measure the Cabibbo-Kobayashi-Maskawa(CKM) matrix element Vtb. The next-to-next-to-leading-order (NNLO) calculation of the single top quark production has many building blocks. In this study, two blocks will be presented: one-loop corrections squared and two-loop corrections interfered with Born. Initially, the one-loop squared contribution at NNLO for single top quark production will be calculated. Before we begin with the calculation of the two-loop corrections to single top quark production, we calculate the QCD form factors of heavy quarks at NNLO, along with the axial vector coupling as a first independent check. A comparison with the relevant literature suggests that this approach is in line with generally accepted procedure. This consistency check provides a proof of the validity of our setup. In the next step, the two-loop corrections to single top quark production will be calculated. After reducing all occurring tensor integrals to scalar integrals, we apply the integration by parts method (IBP) to find the master integrals. This step is a major challenge compared to all similar calculations because of the number of variables in the problem (two Mandelstam variables s and t, the dimension d and the mass of the top quark mt as well as the mass of the W boson mw). Finally, the calculation of the three kinds of topologies – vertex corrections, double boxes and non-planar double boxes – in the two-loop contribution at NNLO calculation will be presented.
Download or read book Measurements of Top Quark Production and Properties at the Tevatron written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this letter, we summarize the latest results of the top-quark production and properties at the Tevatron. We do not include results of the top-quark mass and single top-quark production as they were presented in separate talks. The results of the measurements are mostly consistent with the standard-model predictions. However, by looking at the production asymmetry measured by CDF, one can see a discrepancy in both, $t\bar{t}$ inclusive and lepton-based measurements. D\O\ results of production asymmetry are compatible with the standard-model predictions as well as with the CDF results.
Download or read book Adams After Noon Press Clippings written by and published by . This book was released on 19?? with total page 203 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Finite Lifetime Effects in Top Quark Pair Production at Threshold written by Christoph Josef Reißer and published by Cuvillier Verlag. This book was released on 2008 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Recent Results on Top Quark Physics at written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the most recent measurements on top-quark physics obtained with Tevatron $p\bar{p}$ collisions recorded by the D0 experiment at $\sqrt{s}= 1.96$ TeV. The full Run II data set of 9.7 fb$^{-1}$ is analyzed. Both lepton+jets and dilepton channels of top-quark pair production are used to measure the differential and inclusive cross sections, the forward-backward asymmetries, the top-quark mass, the spin correlations, and the top-quark polarization.
Download or read book Top Quark Physics at the Tevatron written by and published by . This book was released on 2015 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: An overview of recent top quark measurements using the full Run II data set of CDF or D0 at the Tevatron is presented. Results are complementary to the ones at the LHC. Recent measurements of the production cross section of top quarks in strong and electroweak production and of top quark production asymmetries are presented. The latter includes the measurement of the tt-bar production asymmetry by D0 in the dilepton decay channel. Within their uncertainties the results from all these measurements agree with their respective Standard Model expectation. Finally latest updates on measurements of the top quark mass are discussed, which at the time of the conference are the most precise determinations.
Download or read book Top Quark Production at the Tevatron written by and published by . This book was released on 2011 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The top quark is the most recently discovered of the standard model quarks, and because of its very large mass, studies of the top quark and its interactions are important both as tests of the standard model and searches for new phenomena. In this document, recent results of analyses of top quark production, via both the electroweak and strong interactions, from the CDF and D0 experiments are presented. The results included here utilize a dataset corresponding to up to 6 fb−1 of integrated luminosity, slightly more than half of the dataset recorded by each experiment before the Tevatron was shutdown in September 2011.
