Evidence for a Higgs Boson in Tau Decays with the CMS Detector
Evidence for a Higgs Boson in Tau Decays with the CMS Detector

Author: Valentina Dutta

Publisher:

Published: 2014

Total Pages: 185

ISBN-13:

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In this thesis, I describe the search for a Higgs boson through its decay to a pair of tan leptons with the tau-pair subsequently decaying to ail electron, a muon, and neutrinos. The search is performed using data collected from proton-proton collisions by the Compact Muon Solenoid experiment at the Large Hadron Collider, corresponding to 5.0 fb-1 of integrated luminosity recorded at a center-of-mass energy of 7 TeV and 19.7 fb-1 at 8 TeV. The expected significance for a Standard Model Higgs boson signal with a mass of 125 GeV is at the level of 1.2 standard deviations for the electron muon tau-pair decay mode. A mild excess of events is seen above the SM background expectation in this decay mode, consistent with a SM Higgs boson of mass 125 GeV. In combination with results using other tau-pair decay modes, an excess of events above the background expectation is seen at the level of 3.4 standard deviations. This constitutes the first evidence for a Higgs boson to decay to leptons. This thesis also describes an analysis of the data in the context of physics beyond the Standard Model, particularly in the framework of its Minimal Supersymnnetric extension.

Search for Decays of the Higgs Boson Into Muons in P-P Collisions with the CMS Detector
Search for Decays of the Higgs Boson Into Muons in P-P Collisions with the CMS Detector

Author: Luisa Fernanda Chaparro Sierra

Publisher:

Published: 2017

Total Pages:

ISBN-13:

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"In this thesis a search for events in which the recently discovered Higgs boson decays into a pair of muons is presented. The search was performed using the data collected by the CMS experiment at CERN during Run 2 of the LHC accelerator. The data comes from p-p collisions at (sqrt) s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb^-1 . In the Standard Model of Particles and Fields (SM) once the mass of the Higgs boson is known, all its couplings get fixed, including the coupling to muons. Any significant deviations in the experimental results from the values expected from the SM predictions could indicate the onset of new physics. Therefore, it is very important to measure all possible decay channel parameters. The H to (mu) ^+ (mu)^- is the only channel where the Higgs boson couples to the second generation of fermions that could be measured during Run 2 of the LHC. The Higgs coupling to fermions is proportional to the mass of the particles, and since the muons are very light, any measurement in this channel provides valuable information about the Higgs Yukawa coupling to fermions. The small branching ratio of the H to (mu) ^+ (mu)^- decay (2.4 * 10^-4 ) indicates that with the statistics collected by CMS during the Run 2 of the LHC, the expected number of events is also small. Therefore, any improvement in the event selection should be included in the analysis. In this thesis I have focused in recovering events in which the final-state muons might have radiated photons (final-state radiation, FSR) and in correcting the resulting invariant mass distribution. Two techniques were implemented: a cut-based analysis and a multivariate analysis. A study of the impact of the FSR photon recovery in the Higgs mass reconstruction is presented. These studies were done as part of the research activities of the CMS H2Mu Analysis Group."--Tomado del Formato de Documento de Grado.

Discovery Of The Higgs Boson
Discovery Of The Higgs Boson

Author: Aleandro Nisati

Publisher: World Scientific

Published: 2016-08-26

Total Pages: 470

ISBN-13: 981442546X

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The recent observation of the Higgs boson has been hailed as the scientific discovery of the century and led to the 2013 Nobel Prize in physics. This book describes the detailed science behind the decades-long search for this elusive particle at the Large Electron Positron Collider at CERN and at the Tevatron at Fermilab and its subsequent discovery and characterization at the Large Hadron Collider at CERN. Written by physicists who played leading roles in this epic search and discovery, this book is an authoritative and pedagogical exposition of the portrait of the Higgs boson that has emerged from a large number of experimental measurements. As the first of its kind, this book should be of interest to graduate students and researchers in particle physics.

The God Particle
The God Particle

Author: Leon M. Lederman

Publisher: Houghton Mifflin Harcourt

Published: 2006

Total Pages: 452

ISBN-13: 9780618711680

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A fascinating tour of particle physics from Nobel Prize winner Leon Lederman. At the root of particle physics is an invincible sense of curiosity. Leon Lederman embraces this spirit of inquiry as he moves from the Greeks' earliest scientific observations to Einstein and beyond to chart this unique arm of scientific study. His survey concludes with the Higgs boson, nicknamed the God Particle, which scientists hypothesize will help unlock the last secrets of the subatomic universe, quarks and all--it's the dogged pursuit of this almost mystical entity that inspires Lederman's witty and accessible history.

Search for Higgs Boson Decays to Charm Quarks with the ATLAS Experiment and Development of Novel Silicon Pixel Detectors
Search for Higgs Boson Decays to Charm Quarks with the ATLAS Experiment and Development of Novel Silicon Pixel Detectors

Author: Maria Mironova

Publisher: Springer Nature

Published: 2023-07-20

Total Pages: 206

ISBN-13: 3031362209

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This book explores the Higgs boson and its interactions with fermions, as well as the detector technologies used to measure it. The Standard Model of Particle Physics has been a groundbreaking theory in our understanding of the fundamental properties of the universe, but it is incomplete, and there are significant hints which require new physics. The discovery of the Higgs boson in 2012 was a substantial confirmation of the Standard Model, but many of its decay modes remain elusive. This book presents the latest search for Higgs boson decays into c-quarks using a proton-proton collision dataset collected by the ATLAS experiment at the Large Hadron Collider (LHC). This decay mode has yet to be observed and requires advanced machine learning algorithms to identify c-quarks in the experiment. The results provide an upper limit on the rate of Higgs boson decays to c-quarks and a direct measurement of the Higgs boson coupling strength to c-quarks. The book also discusses the future of particle physics and the need for significant improvements to the detector to cope with increased radiation damage and higher data rates at the High-Luminosity LHC. It presents the characterization of the ATLAS pixel detector readout chip for the inner detector upgrade (ITk). The chip was subjected to irradiations using X-rays and protons to simulate the radiation environment at the HL-LHC. The tests showed that all readout chip components, including the digital logic and analogue front-end, are sufficiently radiation-tolerant to withstand the expected radiation dose. Finally, this book describes monolithic pixel detectors as a possible technology for future pixel detectors. This book is ideal for individuals interested in exploring particle physics, the Higgs boson, and the development of silicon pixel detectors.

Electroweak Physics and Evidence for a Higgs Boson Decaying to a Pair of Tau Leptons with the CMS Detector
Electroweak Physics and Evidence for a Higgs Boson Decaying to a Pair of Tau Leptons with the CMS Detector

Author: Aram Apyan

Publisher:

Published: 2017

Total Pages: 170

ISBN-13:

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.Studies of the electroweak interactions using final states with leptons in proton-proton collisions at the Large Hadron Collider at [square root of] s = 7 TeV, [square root of] s = 8 TeV, and [square root of] s = 13 TeV center-of-mass energies are described. Measurements of total inclusive and fiducial W and Z boson production cross sections and their ratios are performed. The W and Z bosons are observed via their decays to electrons and muons. An indirect determination of the total width of the W boson and the B(W --> lv) from the measured cross section ratios is described. The discovery of a new boson with a mass of 125 GeV at the Large Hadron Collider in 2012 sheds a new light on understanding the nature of electroweak symmetry breaking. A question of great significance is whether the new field couples to fermions through a Yukawa coupling interaction predicted in the standard model of particles. Evidence of the 125 GeV Higgs boson decay to a pair of tau leptons with an observed significance of 3.1 standard deviations is established. The nature of the Higgs sector is probed through searches for neutral resonances decaying to a pair of tau leptons in gluon-fusion and b-quark associated production modes with no observation of a significant excess. In addition, the feasibility of measuring the standard model Higgs boson self-coupling with an expected data sample corresponding to an integrated luminosity of 3000 fb-1 is studied.

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.