Study of the Spin and Parity of the Higgs Boson in Diboson Decays with the ATLAS Detector

Study of the Spin and Parity of the Higgs Boson in Diboson Decays with the ATLAS Detector

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Published: 2015

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Studies of the spin, parity and tensor couplings of the Higgs boson in the H→ZZ*→4l, H→WW*→e[nu][mu][nu] and H→[gamma][gamma] decay processes at the LHC are presented. The investigations are based on 25fb-1 of pp collision data collected by the ATLAS experiment at √s=7 TeV and √s=8 TeV. The Standard Model (SM) Higgs boson hypothesis, corresponding to the quantum numbers JP=0+, is tested against several alternative spin scenarios, including non-SM spin-0 and spin-2 models with universal and non-universal couplings to fermions and vector bosons. All tested alternative models are excluded in favour of the SM Higgs boson hypothesis at more than 99.9 % confidence level. Using the H→ZZ*→4l and H→WW*→e[nu][mu][nu] decays, the tensor structure of the interaction between the spin-0 boson and the SM vector bosons is also investigated. The observed distributions of variables sensitive to the non SM tensor couplings are compatible with the SM predictions and constraints on the non SM couplings are derived.


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.


Studies of CP-Violation in Charmless Three-Body b-Hadron Decays

Studies of CP-Violation in Charmless Three-Body b-Hadron Decays

Author: Daniel O'Hanlon

Publisher: Springer

Published: 2018-11-02

Total Pages: 225

ISBN-13: 3030022064

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This book highlights two essential analyses of data collected during the LHCb experiment, based on the Large Hadron Collider at CERN. The first comprises the first observation and studies of matter-antimatter asymmetries in two three-body b-baryon decays, paving the way for more precise measurements of the relatively unknown decay properties of b-baryon decays. The second is an analysis of a charged B meson decay to three charged pions, where previously large matter-antimatter asymmetries were observed in a model-independent analysis. Here a model of the decay amplitude is constructed using the unitarity-conserving ‘K-matrix’ model for the scalar contributions, so as to gain an understanding of how the previously observed matter-antimatter asymmetries arise; further, the model’s construction yields the most precise and comprehensive study of this decay mode to date.


Determination of Spin and Parity of the Higgs Boson in the WW* 2!e [nu] [mu] [nu] Decay Channel with the ATLAS Detector

Determination of Spin and Parity of the Higgs Boson in the WW* 2!e [nu] [mu] [nu] Decay Channel with the ATLAS Detector

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Published: 2015

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Research of the spin and parity quantum numbers of the Higgs boson in the WW* → e[nu][mu][nu] final state are presented, based on proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb-1 at a centre-of-mass energy of √s=8 TeV. The Standard Model spin-parity JCP=0++ hypothesis is compared with alternative hypotheses for both spin and CP. The case where the observed resonance is a mixture of the Standard-Model-like Higgs boson and CP-even (JCP=0++) or CP-odd (JCP=0+-) Higgs boson in scenarios beyond the Standard Model is also studied. The data are found to be consistent with the Standard Model prediction and limits are placed on alternative spin and CP hypotheses, including CP mixing in different scenarios.


Physics with Photons Using the ATLAS Run 2 Data

Physics with Photons Using the ATLAS Run 2 Data

Author: Stefano Manzoni

Publisher: Springer

Published: 2019-08-02

Total Pages: 265

ISBN-13: 3030243702

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The work presented in this book is based on the proton-proton collision data from the Large Hadron Collider at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector in 2015 and 2016. The research program of the ATLAS experiment includes the precise measurement of the parameters of the Standard Model, and the search for signals of physics beyond the SM. Both these approaches are pursued in this thesis, which presents two different analyses: the measurement of the Higgs boson mass in the di-photon decay channel, and the search for production of supersymmetric particles (gluinos, squarks or winos) in a final state containing two photons and missing transverse momentum. Finally, ATLAS detector performance studies, which are key ingredients for the two analyses outlined before, are also carried out and described.


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.


Particle Physics At The Year Of Light - Proceedings Of The Seventeenth Lomonosov Conference On Elementary Particle Physics

Particle Physics At The Year Of Light - Proceedings Of The Seventeenth Lomonosov Conference On Elementary Particle Physics

Author: Alexander I Studenikin

Publisher: World Scientific

Published: 2017-04-17

Total Pages: 595

ISBN-13: 9813224576

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The volume of these proceedings is devoted to a wide variety of items, both in theory and experiment, of particle physics such as electroweak theory, fundamental symmetries, tests of the standard model and beyond, neutrino and astroparticle physics, hadron physics, gravitation and cosmology, physics at the present and future accelerator.


Discovery and Measurement of the Higgs Boson in the WW Decay Channel

Discovery and Measurement of the Higgs Boson in the WW Decay Channel

Author: David Hall

Publisher: Springer

Published: 2015-06-15

Total Pages: 175

ISBN-13: 3319199897

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This thesis describes the stand-alone discovery and measurement of the Higgs boson in its decays to two W bosons using the Run-I ATLAS dataset. This is the most precise measurement of gluon-fusion Higgs boson production and is among the most significant results attained at the LHC. The thesis provides an exceptionally clear exposition on a complicated analysis performed by a large team of researchers. Aspects of the analysis performed by the author are explained in detail; these include new methods for evaluating uncertainties on the jet binning used in the analysis and for estimating the background due to associated production of a W boson and an off-shell photon. The thesis also describes a measurement of the WW cross section, an essential background to Higgs boson production. The primary motivation of the LHC was to prove or disprove the existence of the Higgs boson. In 2012, CERN announced this discovery and the resultant ATLAS publication contained three decay channels: gg, ZZ, and WW.


Newphysicsfrontiersinthelhc-2era,the-proceedingsofthe54thcourseoftheinternationalschoolofsubnuclearphysics

Newphysicsfrontiersinthelhc-2era,the-proceedingsofthe54thcourseoftheinternationalschoolofsubnuclearphysics

Author: Zichichi Antonino

Publisher: World Scientific

Published: 2019-06-24

Total Pages: 500

ISBN-13: 9811206864

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In June 2016, a group of 167 physicists from 31 countries have met in Erice to participate in the 54th Course of the International School of Subnuclear Physics. The main focus of this year's course has been the new frontiers of Physics in the LHC-2 Era and in all labs the world over, as well as the new frontiers in related fields.