A Beauty-ful Boson
A Beauty-ful Boson

Author: Giulia Di Gregorio

Publisher: Springer Nature

Published: 2023-01-01

Total Pages: 229

ISBN-13: 3031200136

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The analysis described in this thesis is the search for the Higgs boson, decaying into bb pair, in the associated production with a vector boson, in the extreme Higgs boson transverse momentum region where the Higgs boson is reconstructed using the large-R jet technique. The use of the large-R jets allows to add a part of the phase space unexplored so far, which is particularly sensitive to possible new physics. The analysed data have been collected at LHC by the ATLAS detector between 2015 and 2018 at a centre-of-mass energy of √s = 13 TeV. The same dataset has been used to perform the differential pp → ZH and pp → WH cross-section measurements used to extract the information on the Higgs couplings and to put limits on Beyond the Standard Model effects. Furthermore the analysis has been re-used to perform a cross-section measurement of the diboson ZZ and WZ processes because the diboson and the Higgs processes have a similar topology. For the first time the ZZ(bb) and WZ(bb) cross-sections are measured at √s = 13 TeV and the observed cross-section measurements are consistent with the Standard Model predictions.

A Search for the Standard Model Higgs Boson Produced in Association with a $W$ Boson
A Search for the Standard Model Higgs Boson Produced in Association with a $W$ Boson

Author:

Publisher:

Published: 2011

Total Pages: 177

ISBN-13:

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We present a search for a standard model Higgs boson produced in association with a W boson using data collected with the CDF II detector from p$ar{p}$ collisions at √s = 1.96 TeV. The search is performed in the WH → lvb$ar{b}$ channel. The two quarks usually fragment into two jets, but sometimes a third jet can be produced via gluon radiation, so we have increased the standard two-jet sample by including events that contain three jets. We reconstruct the Higgs boson using two or three jets depending on the kinematics of the event. We find an improvement in our search sensitivity using the larger sample together with this multijet reconstruction technique. Our data show no evidence of a Higgs boson, so we set 95% confidence level upper limits on the WH production rate. We set limits between 3.36 and 28.7 times the standard model prediction for Higgs boson masses ranging from 100 to 150 GeV/c2.

Search for the Standard Model Higgs Boson in the H → ZZ → l + l - qq Decay Channel at CMS
Search for the Standard Model Higgs Boson in the H → ZZ → l + l - qq Decay Channel at CMS

Author: Francesco Pandolfi

Publisher: Springer Science & Business Media

Published: 2013-08-15

Total Pages: 137

ISBN-13: 3319009036

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The theoretical foundations of the Standard Model of elementary particles relies on the existence of the Higgs boson, a particle which has been revealed for the first time by the experiments run at the Large Hadron Collider (LHC) in 2012. As the Higgs boson is an unstable particle, its search strategies were based on its decay products. In this thesis, Francesco Pandolfi conducted a search for the Higgs boson in the H → ZZ → l + l - qq Decay Channel with 4.6 fb -1 of 7 TeV proton-proton collision data collected by the Compact Muon Solenoid (CMS) experiment. The presence of jets in the final state poses a series of challenges to the experimenter: both from a technical point of view, as jets are complex objects and necessitate of ad-hoc reconstruction techniques, and from an analytical one, as backgrounds with jets are copious at hadron colliders, therefore analyses must obtain high degrees of background rejection in order to achieve competitive sensitivity. This is accomplished by following two directives: the use of an angular likelihood discriminant, capable of discriminating events likely to originate from the decay of a scalar boson from non-resonant backgrounds, and by using jet parton flavor tagging, selecting jets compatible with quark hadronization and discarding jets more likely to be initiated by gluons. The events passing the selection requirements in 4.6 fb -1 of data collected by the CMS detector are examined, in the search of a possible signal compatible with the decay of a heavy Higgs boson. The thesis describes the statistical tools and the results of this analysis. This work is a paradigm for studies of the Higgs boson with final states with jets. The non-expert physicists will enjoy a complete and eminently readable description of a proton-proton collider analysis. At the same time, the expert reader will learn the details of the searches done with jets at CMS.

The Higgs Boson
The Higgs Boson

Author: Scientific American Editors

Publisher: Scientific American

Published: 2012-09-30

Total Pages: 467

ISBN-13: 1466824131

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The Higgs Boson: Searching for the God Particle by the Editors of Scientific American Updated 2017 Edition! For the fifth anniversary of one of the biggest discoveries in physics, we’ve updated this eBook to include our continuing analysis of the discovery, of the questions it answers and those it raises. As the old adage goes, where there’s smoke, there’s fire. Where there is effect, there must be cause. The planet Neptune was found in 1846 because the mathematics of Newton's laws, when applied to the orbit of Uranus, said some massive body had to be there. Astronomers eventually found it, using the best telescopes available to peer into the sky. This same logic is applied to the search for the Higgs boson. One consequence of the prevailing theory of physics, called the Standard Model, is that there has to be some field that gives particles their particular masses. With that there has to be a corresponding particle, made by creating waves in the field, and this is the Higgs boson, the so-called God particle. This eBook chronicles the search – and demonstrates the power of a good theory. Based on the Standard Model, physicists believed something had to be there, but it wasn't until the Large Hadron Collider was built that anyone could see evidence of the Higgs – and finally in July 2012, they did. A Higgs-like particle was found near the energies scientists expected to find it. Now, armed with better evidence and better questions, the scientific process continues. This eBook gathers the best reporting and analysis from Scientific American to explain that process – the theories, the search, the ongoing questions. In essence, everything you need to know to separate Higgs from hype.

The Higgs Boson Produced With Top Quarks in Fully Hadronic Signatures
The Higgs Boson Produced With Top Quarks in Fully Hadronic Signatures

Author: Daniel Salerno

Publisher: Springer Nature

Published: 2019-10-25

Total Pages: 207

ISBN-13: 3030312577

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The work presented in this PhD dissertation is the first search at CMS for Higgs bosons produced in association with top quarks (ttH) in a final state consisting of only jets. The results presented in this book uncover a new class of ttH events that will help us elucidate our understanding of the Yukawa sector interactions between the Higgs boson and the top quark. Despite this being the most common decay signature for ttH, a large contamination of SM backgrounds makes it the most challenging for extracting a signal from data. The PhD thesis presents many sophisticated tools and techniques that were developed in order to overcome these challenges. These tools pave the way for future analyses to investigate other standard model and beyond-standard model physics.

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.

A Search for the Standard Model Higgs Boson Produced in Association with a W Boson
A Search for the Standard Model Higgs Boson Produced in Association with a W Boson

Author: Martin J. Frank

Publisher:

Published: 2011

Total Pages:

ISBN-13:

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We present a search for a standard model Higgs boson produced in association with a W boson using data collected with the CDF II detector from proton/antiproton collisions at a center of mass energy of 1.96 TeV. The search is performed in the WH channel where the W boson decays leptonically and the Higgs boson decays to a bottom/antibottom quark pair. The two quarks usually fragment into two jets, but sometimes a third jet can be produced via gluon radiation, so we have increased the standard two-jet sample by including events that contain three jets. We reconstruct the Higgs boson using two or three jets depending on the kinematics of the event. We find an improvement in our search sensitivity using the larger sample together with this multijet reconstruction technique. Our data show no evidence of a Higgs boson, so we set 95% confidence level upper limits on the WH production rate. We set limits between 3.36 and 28.7 times the standard model prediction for Higgs boson masses ranging from 100 to 150 GeV/c^2.

Search for the Standard Model Higgs Boson in Association with a W Boson at
Search for the Standard Model Higgs Boson in Association with a W Boson at

Author:

Publisher:

Published: 2013

Total Pages: 274

ISBN-13:

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I present a search for the standard model Higgs boson, H, produced in association with a W boson in data events containing a charged lepton (electron or muon), missing energy, and two or three jets. The data analysed correspond to 9.7 fb-1 of integrated luminosity collected at a center-of-momentum energy of √s = 1.96 TeV with the D0 detector at the Fermilab Tevatron p$ar{p}$ collider. This search uses algorithms to identify the signature of bottom quark production and multivariate techniques to improve the purity of H → b$ar{b}$ production. We validate our methodology by measuring WZ and ZZ production with Z → b$ar{b}$ and find production rates consistent with the standard model prediction. For a Higgs boson mass of 125 GeV, we determine a 95% C.L. upper limit on the production of a standard model Higgs boson of 4.8 times the standard model Higgs boson production cross section, while the expected limit is 4.7 times the standard model production cross section. I also present a novel method for improving the energy resolution for charged particles within hadronic signatures. This is achieved by replacing the calorimeter energy measurement for charged particles within a hadronic signature with the tracking momentum measurement. This technique leads to a ̃20% improvement in the jet energy resolution, which yields a ̃7% improvement in the reconstructed dijet mass width for H → b$ar{b}$ events. The improved energy calculation leads to a ̃5% improvement in our expected 95% C.L. upper limit on the Higgs boson production cross section.