Search for tt̄H Production in the H → bb̅ Decay Channel
Search for tt̄H Production in the H → bb̅ Decay Channel

Author: Marcel Rieger

Publisher: Springer Nature

Published: 2021-02-25

Total Pages: 217

ISBN-13: 3030653803

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In 1964, a mechanism explaining the origin of particle masses was proposed by Robert Brout, François Englert, and Peter W. Higgs. 48 years later, in 2012, the so-called Higgs boson was discovered in proton-proton collisions recorded by experiments at the LHC. Since then, its ability to interact with quarks remained experimentally unconfirmed. This book presents a search for Higgs bosons produced in association with top quarks tt̄H in data recorded with the CMS detector in 2016. It focuses on Higgs boson decays into bottom quarks H → bb̅ and top quark pair decays involving at least one lepton. In this analysis, a multiclass classification approach using deep learning techniques was applied for the first time. In light of the dominant background contribution from tt̄ production, the developed method proved to achieve superior sensitivity with respect to existing techniques. In combination with searches in different decay channels, the presented work contributed to the first observations of tt̄H production and H → bb̅ decays.

ATLAS Measurements of the Higgs Boson Coupling to the Top Quark in the Higgs to Diphoton Decay Channel
ATLAS Measurements of the Higgs Boson Coupling to the Top Quark in the Higgs to Diphoton Decay Channel

Author: Jennet Elizabeth Dickinson

Publisher: Springer Nature

Published: 2021-11-16

Total Pages: 233

ISBN-13: 3030863689

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During Run 2 of the Large Hadron Collider, the ATLAS experiment recorded proton-proton collision events at 13 TeV, the highest energy ever achieved in a collider. Analysis of this dataset has provided new opportunities for precision measurements of the Higgs boson, including its interaction with the top quark. The Higgs-top coupling can be directly probed through the production of a Higgs boson in association with a top-antitop quark pair (ttH). The Higgs to diphoton decay channel is among the most sensitive for ttH measurements due to the excellent diphoton mass resolution of the ATLAS detector and the clean signature of this decay. Event selection criteria were developed using novel Machine Learning techniques to target ttH events, yielding a precise measurement of the ttH cross section in the diphoton channel and a 6.3 $\sigma$ observation of the ttH process in combination with other decay channels, as well as stringent limits on CP violation in the Higgs-top coupling.

A Boson Learned from its Context, and a Boson Learned from its End
A Boson Learned from its Context, and a Boson Learned from its End

Author: Jeffrey Roskes

Publisher: Springer Nature

Published: 2020-11-19

Total Pages: 144

ISBN-13: 3030580113

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This thesis develops fundamental ideas and advanced techniques for studying the Higgs boson’s interactions with the known matter and force particles. The Higgs boson appears as an excitation of the Higgs field, which permeates the vacuum. Several other phenomena in our Universe, such as dark energy, dark matter, and the abundance of matter over antimatter, remain unexplained. The Higgs field may prove to be the connection between our known world and the “dark” world, and studies of the Higgs boson's interactions are essential to reveal possible new phenomena. The unique feature of this work is simultaneous measurement of the Higgs boson’s associated production (its context, to use the language of the title) and its decay (its end), while allowing for multiple parameters sensitive to new phenomena. This includes computer simulation with Monte Carlo techniques of the complicated structure of the Higgs boson interactions, the matrix-element calculation of per-event likelihoods for optimal observables, and advanced fitting methods with hundreds of intricate components that cover all possible parameters and quantum mechanical interference. This culminates in the most advanced analysis of LHC data in the multi-parameter approach to Higgs physics in its single golden four-lepton decay channel to date. Optimization of the CMS detector’s silicon-based tracking system, essential for these measurements, is also described.

Standard Theory Of Particle Physics, The: Essays To Celebrate Cern's 60th Anniversary
Standard Theory Of Particle Physics, The: Essays To Celebrate Cern's 60th Anniversary

Author: Luciano Maiani

Publisher: World Scientific

Published: 2016-08-25

Total Pages: 484

ISBN-13: 9814733520

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'The editors make a good point in claiming the time has come to upgrade the Standard Model into the ‘Standard Theory’ of particle physics, and I think this book deserves a place in the bookshelves of a broad community, from the scientists and engineers who contributed to the progress of high-energy physics to younger physicists, eager to learn and enjoy the corresponding inside stories.'Carlos LourençoCERN CourierThe book gives a quite complete and up-to-date picture of the Standard Theory with an historical perspective, with a collection of articles written by some of the protagonists of present particle physics. The theoretical developments are described together with the most up-to-date experimental tests, including the discovery of the Higgs Boson and the measurement of its mass as well as the most precise measurements of the top mass, giving the reader a complete description of our present understanding of particle physics.

The Standard Theory of Particle Physics
The Standard Theory of Particle Physics

Author: Luciano Maiani

Publisher: World Scientific Publishing Company

Published: 2016-08-25

Total Pages: 483

ISBN-13: 9814733512

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The book gives a quite complete and up-to-date picture of the Standard Theory with an historical perspective, with a collection of articles written by some of the protagonists of present particle physics. The theoretical developments are described together with the most up-to-date experimental tests, including the discovery of the Higgs Boson and the measurement of its mass as well as the most precise measurements of the top mass, giving the reader a complete description of our present understanding of particle physics.

Conformal Field Theory
Conformal Field Theory

Author: Philippe Francesco

Publisher: Springer Science & Business Media

Published: 2012-12-06

Total Pages: 908

ISBN-13: 1461222567

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Filling an important gap in the literature, this comprehensive text develops conformal field theory from first principles. The treatment is self-contained, pedagogical, and exhaustive, and includes a great deal of background material on quantum field theory, statistical mechanics, Lie algebras and affine Lie algebras. The many exercises, with a wide spectrum of difficulty and subjects, complement and in many cases extend the text. The text is thus not only an excellent tool for classroom teaching but also for individual study. Intended primarily for graduate students and researchers in theoretical high-energy physics, mathematical physics, condensed matter theory, statistical physics, the book will also be of interest in other areas of theoretical physics and mathematics. It will prepare the reader for original research in this very active field of theoretical and mathematical physics.

Modern Supersymmetry
Modern Supersymmetry

Author: John Terning

Publisher: OUP Oxford

Published: 2009-01-15

Total Pages: 339

ISBN-13: 0191565490

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The book begins with a brief review of supersymmetry, and the construction of the minimal supersymmetric standard model and approaches to supersymmetry breaking. General non-perturbative methods are also reviewed leading to the development of holomorphy and the Affleck-Dine-Seiberg superpotential as powerful tools for analysing supersymmetric theories. Seiberg duality is discussed in detail, with many example applications provided, with special attention paid to its use in understanding dynamical supersysmmetry breaking. The Seiberg-Witten theory of monopoles is introduced through the analysis of simpler N=1 analogues. Superconformal field theories are described along with the most recent development known as "amaximization". Supergravity theories are examined in 4, 10, and 11 dimensions, allowing for a discussion of anomaly and gaugino mediation, and setting the stage for the anti- de Sitter/conformal field theory correspondence. This book is unique in containing an overview of the important developments in supersymmetry since the publication of "Suppersymmetry and Supergravity" by Wess and Bagger. It also strives to cover topics that are of interest to both formal and phenomenological theorists.

Quantum (Un)speakables
Quantum (Un)speakables

Author: R.A. Bertlmann

Publisher: Springer Science & Business Media

Published: 2002-07-27

Total Pages: 512

ISBN-13: 9783540427568

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This outstanding collection of essays in commemoration of John S. Bell is the result of the "Quantum (Un)speakables" conference organised by the University of Vienna. The title was taken from a famous note written by John Bell during the "Schrödinger Symposium" of 1987. The book leads the reader from the foundations of quantum mechanics to quantum entanglement, quantum cryptography, and quantum information, and is written for all those who need more insight into this new area of physics.

Measurements of Higgs Boson Properties in Proton-Proton Collisions at √s =7, 8 and 13 TeV at the CERN Large Hadron Collider
Measurements of Higgs Boson Properties in Proton-Proton Collisions at √s =7, 8 and 13 TeV at the CERN Large Hadron Collider

Author: Ulascan Sarica

Publisher: Springer

Published: 2020-10-09

Total Pages: 103

ISBN-13: 9783030254766

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This thesis documents the measurement of lifetime, width, mass, and couplings to two electroweak bosons of the recently-discovered Higgs boson using data from the CMS experiment at the Large Hadron Collider. Both on-shell (at the mass of around 125 GeV) and off-shell (above 200 GeV) Higgs boson production is studied and an excess of off-shell production with significance above two standard deviations is observed for the first time. The latter is a qualitative new way to study the Higgs field, responsible for generation of mass of all the known elementary particles. In addition, phenomenological tools have been developed with the Monte Carlo event generator and matrix element techniques for an optional analysis of LHC data. Optimization of the CMS data with careful alignment of the silicon tracker is also presented.

Higgs, Supersymmetry and Dark Matter After Run I of the LHC
Higgs, Supersymmetry and Dark Matter After Run I of the LHC

Author: Béranger Dumont

Publisher: Springer

Published: 2016-09-30

Total Pages: 0

ISBN-13: 9783319449555

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This work was nominated as an outstanding PhD thesis by the LPSC, Université Grenoble Alpes, France. The LHC Run 1 was a milestone in particle physics, leading to the discovery of the Higgs boson, the last missing piece of the so-called "Standard Model" (SM), and to important constraints on new physics, which challenge popular theories like weak-scale supersymmetry. This thesis provides a detailed account of the legacy of the LHC Run 1 ≤¥regarding these aspects. First, the SM and the need for its extension are presented in a concise yet revealing way. Subsequently, the impact of the LHC Higgs results on scenarios of new physics is assessed in detail, including a careful discussion of the relevant uncertainties. Two approaches are considered: generic modifications of the Higgs couplings, possibly arising from extended Higgs sectors or higher-dimensional operators; and tests of specific new physics models. Lastly, the implications of the null results of the searches for new physics are discussed with a particular focus on supersymmetric dark matter candidates. Here as well, two approaches are presented: the "simplified models" approach, and recasting by event simulation. This thesis stands out for its educational approach, its clear language and the depth of the physics discussion. The methods and tools presented offer readers essential practical tools for future research.