Observation And Measurement Of Higgs Boson Decays To Ww With The Atlas Detector
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Discovery And Measurement Of The Higgs Boson In The Ww Decay Channel
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Author : David Hall
language : en
Publisher: Springer
Release Date : 2015-06-15
Discovery And Measurement Of The Higgs Boson In The Ww Decay Channel written by David Hall and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-06-15 with Science categories.
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.
Observation And Measurement Of Higgs Boson Decays To Ww With The Atlas Detector
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Author :
language : en
Publisher:
Release Date : 2015
Observation And Measurement Of Higgs Boson Decays To Ww With The Atlas Detector written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
We report the observation of Higgs boson decays to WW* based on an excess over background of 6.1 standard deviations in the dilepton final state, where the Standard Model expectation is 5.8 standard deviations. Evidence for the vector-boson fusion (VBF) production process is obtained with a significance of 3.2 standard deviations. The results are obtained from a data sample corresponding to an integrated luminosity of 25 fb-1 from [arrow]"=7 and 8 TeV pp collisions recorded by the ATLAS detector at the LHC. For a Higgs boson mass of 125.36 GeV, the ratio of the measured value to the expected value of the total production cross section times branching fraction is 1.09+0.16-0.15(stat)+0.17-0.14(syst). The corresponding ratios for the gluon fusion and vector-boson fusion production mechanisms are 1.02 " 0.19(stat)+0.22-0.18(syst) and 1.27+0.44-0.40(stat)+0.30-0.21(syst), respectively. At [arrow]"=8 TeV, the total production cross sections are measured to be [sigma](gg 2!>H 2!WW*)=4.6"0.9(stat)+0.8-0.7(syst) pb and [sigma](VBF H 2!W*)=0.51+0.17-0.15(stat)+0.13-0.08(syst) pb. The fiducial cross section is determined for the gluon-fusion process in exclusive final states with 0 or one associated jet.
Higgs Boson Decays Into A Pair Of Bottom Quarks
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Author : Cecilia Tosciri
language : en
Publisher: Springer Nature
Release Date : 2021-10-22
Higgs Boson Decays Into A Pair Of Bottom Quarks written by Cecilia Tosciri and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-10-22 with Science categories.
The discovery in 2012 of the Higgs boson at the Large Hadron Collider (LHC) represents a milestone for the Standard Model (SM) of particle physics. Most of the SM Higgs production and decay rates have been measured at the LHC with increased precision. However, despite its experimental success, the SM is known to be only an effective manifestation of a more fundamental description of nature. The scientific research at the LHC is strongly focused on extending the SM by searching, directly or indirectly, for indications of New Physics. The extensive physics program requires increasingly advanced computational and algorithmic techniques. In the last decades, Machine Learning (ML) methods have made a prominent appearance in the field of particle physics, and promise to address many challenges faced by the LHC. This thesis presents the analysis that led to the observation of the SM Higgs boson decay into pairs of bottom quarks. The analysis exploits the production of a Higgs boson associated with a vector boson whose signatures enable efficient triggering and powerful background reduction. The main strategy to maximise the signal sensitivity is based on a multivariate approach. The analysis is performed on a dataset corresponding to a luminosity of 79.8/fb collected by the ATLAS experiment during Run-2 at a centre-of-mass energy of 13 TeV. An excess of events over the expected background is found with an observed (expected) significance of 4.9 (4.3) standard deviation. A combination with results from other \Hbb searches provides an observed (expected) significance of 5.4 (5.5). The corresponding ratio between the signal yield and the SM expectation is 1.01 +- 0.12 (stat.)+ 0.16-0.15(syst.). The 'observation' analysis was further extended to provide a finer interpretation of the V H(H → bb) signal measurement. The cross sections for the VH production times the H → bb branching ratio have been measured in exclusive regions of phase space. These measurements are used to search for possible deviations from the SM with an effective field theory approach, based on anomalous couplings of the Higgs boson. The results of the cross-section measurements, as well as the constraining of the operators that affect the couplings of the Higgs boson to the vector boson and the bottom quarks, have been documented and discussed in this thesis. This thesis also describes a novel technique for the fast simulation of the forward calorimeter response, based on similarity search methods. Such techniques constitute a branch of ML and include clustering and indexing methods that enable quick and efficient searches for vectors similar to each other. The new simulation approach provides optimal results in terms of detector resolution response and reduces the computational requirements of a standard particles simulation.
Charming Decays Of The Higgs Z And W Bosons
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Author : Spandan Mondal
language : en
Publisher: Springer Nature
Release Date : 2025-06-13
Charming Decays Of The Higgs Z And W Bosons written by Spandan Mondal and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2025-06-13 with Science categories.
This book presents searches for the Higgs boson, Z boson, and W boson decaying into charm quark(s) performed with proton-proton collision data at √s = 13TeV collected by the CMS experiment at the LHC, CERN, corresponding to an integrated luminosity of 138 fb−1 and recorded between 2016 and 2018. The searches are carried out using events in which the Higgs/Z/W boson is produced in association with a leptonically-decaying Z or W boson. This thesis also discusses a novel calibration algorithm for charm jet identification that enables maximal use of the available information related to charm jets. The new method is used to correct the entire distribution expected as output when jet flavour identification algorithms are applied to jets of different flavours. The calibrated results improve over traditional efficiency measurements and help enhance the sensitivities of the Higgs, Z, and W searches. This book primarily reports on the so-called resolved-jet topology of the Higgs/Z/W boson searches, where the boson candidates are reconstructed using two separate small-radius (AK4) jets. Upon statistically combining the results of the resolved-jet search with a complementary merged-jet approach, the observed (expected) upper limit on the Higgs decay to charm quarks corresponds to 14 (7.6) times the Standard Model expectation at the 95% CL which is the most stringent direct limit to date. A significance of 5.7σ (5.9σ) over the background-only prediction is observed (expected) in case of the search for charmed Z boson decays. Only the resolved-jet topology is used in the search for charmed W decays and the observed (expected) significance is 5.6σ (5.7σ) over the background-only prediction. These mark the first observations of charmed decays of the Z and W bosons at a hadron collider experiment.
The Higgs Boson Discovery At The Large Hadron Collider
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Author : Roger Wolf
language : en
Publisher: Springer
Release Date : 2015-05-18
The Higgs Boson Discovery At The Large Hadron Collider written by Roger Wolf and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-05-18 with Science categories.
This book provides a comprehensive overview of the field of Higgs boson physics. It offers the first in-depth review of the complete results in connection with the discovery of the Higgs boson at CERN’s Large Hadron Collider and based on the full dataset for the years 2011 to 2012. The fundamental concepts and principles of Higgs physics are introduced and the important searches prior to the advent of the Large Hadron Collider are briefly summarized. Lastly, the discovery and first mensuration of the observed particle in the course of the CMS experiment are discussed in detail and compared to the results obtained in the ATLAS experiment.
Electroweak Physics At The Lhc
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Author : Matthias U. Mozer
language : en
Publisher: Springer
Release Date : 2016-03-24
Electroweak Physics At The Lhc written by Matthias U. Mozer and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-03-24 with Science categories.
The book discusses the recent experimental results obtained at the LHC that involve electroweak bosons. The results are placed into an appropriate theoretical and historical context. The work pays special attention to the rising subject of hadronically decaying bosons with high boosts, documenting the state-of-the-art identification techniques and highlighting typical results. The text is not limited to electroweak physics in the strict sense, but also discusses the use of electroweak vector-bosons as tool in the study of other subjects in particle physics, such as determinations of the proton structure or the search for new exotic particles. The book is particularly well suited for graduate students, starting their thesis work on topics that involve electroweak bosons, as the book provides a comprehensive description of phenomena observable at current accelerators as well as a summary of the most relevant experimental techniques.
Physics With Electrons In The Atlas Detector
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Author : Kurt Brendlinger
language : en
Publisher: Springer
Release Date : 2018-01-30
Physics With Electrons In The Atlas Detector written by Kurt Brendlinger and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-01-30 with Science categories.
This thesis presents two production cross-section measurements of pairs of massive bosons using final states with leptons, made with the ATLAS detector at the Large Hadron Collider. The first measurement, performed using data collected in 2012 at center-of-mass energy √ s = 8 TeV, is the first fiducial and differential cross-section measurement of the production of the Higgs Boson when it decays to four charged leptons (electrons or muons). The second measurement is the first fiducial and inclusive production cross-section measurement of WZ pairs at center-of-mass energy √ s = 13 TeV using final states with three charged leptons. A significant portion of the thesis focuses on the methods used to identify electrons from massive boson decay—important for many flagship measurements—and on assessing the efficiency of these particle identification techniques. The chapter discussing the WZ pair cross-section measurement provides a detailed example of an estimate of lepton background in the context of an analysis with three leptons in the final state.
Physics With Photons Using The Atlas Run 2 Data
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Author : Stefano Manzoni
language : en
Publisher: Springer
Release Date : 2019-08-02
Physics With Photons Using The Atlas Run 2 Data written by Stefano Manzoni and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-08-02 with Science categories.
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 Tt H Production In The H Bb Decay Channel
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Author : Marcel Rieger
language : en
Publisher: Springer Nature
Release Date : 2021-02-25
Search For Tt H Production In The H Bb Decay Channel written by Marcel Rieger and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-02-25 with Science categories.
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.
Standard Model Measurements With The Atlas Detector
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Author : Jana Nováková
language : en
Publisher: Springer Science & Business Media
Release Date : 2013-08-30
Standard Model Measurements With The Atlas Detector written by Jana Nováková and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-08-30 with Science categories.
This thesis deals with two main procedures performed with the ATLAS detector at the Large Hadron Collider (LHC). The noise description in the hadronic calorimeter TileCal represents a very valuable technical job. The second part presents a fruitful physics analysis - the cross section measurement of the process p+p → Z0 → τ + τ. The Monte Carlo simulations of the TileCal are described in the first part of the thesis, including a detailed treatment of the electronic noise and multiple interactions (so-called pile-up). An accurate description of both is crucial for the reconstruction of e.g. jets or hadronic tau-jets. The second part reports a Standard Model measurement of the Z0 → τ + τ process with the emphasis on the final state with an electron and a hadronically decaying tau-lepton. The Z0 → τ + τ channel forms the dominant background in the search for Higgs bosons decaying into tau lepton pairs, and thus the good understanding achieved here can facilitate more sensitive Higgs detection.