Search For The Higgs Boson In The Tt H H Bb Channel In The Atlas Experiment At The Lhc Using Machine Learning Methods And Synchronization Of The Itk Geometry Description For Simulation And Radiation Studies For The Hl Lhc Atlas Upgrade
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Search For The Higgs Boson In The Tt H H Bb Channel In The Atlas Experiment At The Lhc Using Machine Learning Methods And Synchronization Of The Itk Geometry Description For Simulation And Radiation Studies For The Hl Lhc Atlas Upgrade
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Author : Ziyu Guo
language : en
Publisher:
Release Date : 2019
Search For The Higgs Boson In The Tt H H Bb Channel In The Atlas Experiment At The Lhc Using Machine Learning Methods And Synchronization Of The Itk Geometry Description For Simulation And Radiation Studies For The Hl Lhc Atlas Upgrade written by Ziyu Guo and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
The Higgs-top coupling (top Yukawa coupling) measurement can further test the standardmodel, being much stronger than the ones for the other quarks. The associated production of aHiggs boson with a top quark pair (ttH) allows to do a direct measurement. With the ATLASdetector at the LHC, this thesis presents a search for ttH in the H->bb decay mode, rarelyproduced compared with the tt backgrounds. Both processes have final states with multiple jetsand b-jets making the analysis heavily relying on advanced techniques. The large tt modelinguncertainties are a driving factor of the sensitivity.This thesis searches to increase the ttH (H->bb) sensitivity by exploring machine learningmethods. Using early Run 2 data, boosted decision trees are exploited to firstly solve the jet-parton assignment in the reconstruction of the ttH signal, and in a second step classify ttH andtt. The observed significance under the background only hypothesis is 1.4 standard deviations.Targeting a contribution to the analysis round using full Run 2 data, deep learningtechniques are explored: recurrent neural networks as binary classifier solving reconstructionand classification in one step, physics-expertise-aware deep neural networks exploiting rawfeatures, RNN-based multi-classifier for event categorization, and adversarial neural networkaimed to decrease the tt modeling uncertainty.Coping with the new LHC phase starting in mid-2020's, ATLAS will be upgradedto have a new inner tracker. The author contributes to synchronize its geometry descriptionsindependently implemented and used by simulation and radiation studies, which is importantto validate a radiation estimation.
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.
Atlas Measurements Of The Higgs Boson Coupling To The Top Quark In The Higgs To Diphoton Decay Channel
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Author : Jennet Elizabeth Dickinson
language : en
Publisher: Springer
Release Date : 2022-11-18
Atlas Measurements Of The Higgs Boson Coupling To The Top Quark In The Higgs To Diphoton Decay Channel written by Jennet Elizabeth Dickinson and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022-11-18 with Science categories.
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.
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.
Higgs Boson Production With A Top Quark Pair In The Diphoton Channel Double Higgs Production In The Bb Diphoton Channel And Inner Tracker Upgrade With The Atlas Detector At The Large Hadron Collider
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Author : Alex Zeng Wang
language : en
Publisher:
Release Date : 2023
Higgs Boson Production With A Top Quark Pair In The Diphoton Channel Double Higgs Production In The Bb Diphoton Channel And Inner Tracker Upgrade With The Atlas Detector At The Large Hadron Collider written by Alex Zeng Wang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with categories.
Since the discovery of the Higgs boson in 2012, the diphoton ([gamma][gamma]) decay channel of the Higgs boson has been one of the most potent channels due to the contrast between the smoothly falling background and sharply peaked signal in the diphoton invariant mass. In 2018, with up to 80 fb-1 of data at [square root]s = 13 TeV, ATLAS observed Higgs boson production in association with a pair of top quarks (ttH) with a significance of 5.8 [sigma] by combining measurements in the [gamma][gamma], bb, ZZ, and multi-lepton Higgs decay channels. The ttH production cross-section was measured to be 670 [plus or minus] 90 (stat) +110 -100 (syst) fb. The diphoton channel was one of the main contributors to this result, alone providing a significance of 4.1 [sigma]. With 140 fb-1, a search for non-resonant Higgs pair production in the bb[gamma][gamma] final state was performed. No significant signal was observed and upper limits at 95% confidence level were set. The observed limit on the SM cross-section was 130 fb, or 4.2 times the predicted value. The observed Higgs trilinear coupling modifier was constrained to be between [-1.5, 6.7]. Both the ttH (H [rightwards arrow] [gamma][gamma]) and HH bb[gamma][gamma] analyses will benefit tremendously from the increased statistics expected from the High-Luminosity LHC (HL-LHC). To ensure the continued efficiency of the detector in the harsh HL-LHC environment, ATLAS will install a new Inner Tracker (ITk) consisting of silicon pixel sensors in its innermost layer. At SLAC National Accelerator Laboratory, a variety of electrical tests are performed for the construction of a prototype integrated pixel system, in order to provide early feedback and validation of the ITk design.
Search For The Higgs Boson Produced In Association With Top Quarks With The Cms Detector At The Lhc
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Author : Cristina Martin Perez
language : en
Publisher: Springer
Release Date : 2023-02-10
Search For The Higgs Boson Produced In Association With Top Quarks With The Cms Detector At The Lhc written by Cristina Martin Perez and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-02-10 with Science categories.
In this work, the interaction between the Higgs boson and the top quark is studied with the proton-proton collisions at 13 TeV provided by the LHC at the CMS detector at CERN (Geneva). At the LHC, these particles are produced simultaneously via the associate production of the Higgs boson with one top quark (tH process) or two top quarks (ttH process). Compared to many other possible outcomes of the proton-proton interactions, these processes are very rare, as the top quark and the Higgs boson are the heaviest elementary particles known. Hence, identifying them constitutes a significant experimental challenge. A high particle selection efficiency in the CMS detector is therefore crucial. At the core of this selection stands the Level-1 (L1) trigger system, a system that filters collision events to retain only those with potential interest for physics analysis. The selection of hadronically decaying τ leptons, expected from the Higgs boson decays, is especially demanding due to the large background arising from the QCD interactions. The first part of this thesis presents the optimization of the L1 τ algorithm in Run 2 (2016-2018) and Run 3 (2022-2024) of the LHC. It includes the development of a novel trigger concept for the High-Luminosity LHC, foreseen to start in 2027 and to deliver 5 times the current instantaneous luminosity. To this end, sophisticated algorithms based on machine learning approaches are used, facilitated by the increasingly modern technology and powerful computation of the trigger system. The second part of the work presents the search of the tH and ttH processes with the subsequent decays of the Higgs boson to pairs of τ lepton, W bosons or Z bosons, making use of the data recorded during Run 2. The presence of multiple particles in the final state, along with the low cross section of the processes, makes the search an ideal use case for multivariant discriminants that enhance the selectivity of the signals and reject the overwhelming background contributions. The discriminants presented are built using state-of-the-art machine learning techniques, able to capture the correlations amongst the processes involved, as well as the so-called Matrix Element Method (MEM), which combines the theoretical description of the processes with the detector resolution effects. The level of sophistication of the methods used, along with the unprecedented amount of collision data analyzed, result in the most stringent measurements of the tH and ttH cross sections up to date.
Search For The Higgs Boson In The Tth H Bb Channel And The Identification Of Jets Containing Two B Hadrons With The Atlas Experiment
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Author : Royer Edson Ticse Torres
language : en
Publisher:
Release Date : 2016
Search For The Higgs Boson In The Tth H Bb Channel And The Identification Of Jets Containing Two B Hadrons With The Atlas Experiment written by Royer Edson Ticse Torres and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
In July 2012, CERN announced the discovery of the Higgs boson, the last missing piece of the Standard Model (SM). The Higgs boson was observed in different channels. Precise measurement of its properties is now very important to investigate for possible deviations from the SM. This thesis presents a search for the Higgs boson produced in association with top quarks and decaying to a b quark pair, the ttH(H→bb) channel, using proton-proton collisions at √s = 13 TeV, collected with the ATLAS detector in 2015 and 2016. This document details in particular the full reconstruction of the ttH(H→bb) system and the discrimination between signal and the main background, tt+jets. The ttbb is a subset of the tt+jets backgrounds recent studies show that there is a large fraction of ttbb events with jets containing two b-hadrons. A new algorithm has been developed to discriminate such jets from single b-hadrons jets. The description of this tool is presented in this thesis.
Investigation Of The Discovery Potential Of A Higgs Boson In The Tt H0 H0 Bb Channel With The Atlas Experiment
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Author : C. Bernius
language : en
Publisher:
Release Date : 2010
Investigation Of The Discovery Potential Of A Higgs Boson In The Tt H0 H0 Bb Channel With The Atlas Experiment written by C. Bernius and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
The production of a light Standard Model Higgs boson in association with a top-quark pair at the Large Hadron Collider (LHC) is studied in a simulation of the multipurpose ATLAS experiment. The Higgs boson is assumed to decay into a b\bar{b} pair, and the top-quark pair to decay semi-leptonically. The main background process for this channel is the production of t\bar{t} events, which can be divided into reducible and irreducible components. In the process of generating these components separately, an overlap of events is created through the addition of b-quarks to t\bar{t} events via parton showering in the t\bar{t}X sample. These events are already included in the matrix-element cross-section calculation for the t\bar{t}b\bar{b} sample. A new procedure for the overlap removal is presented in this thesis. Two analyses are studied, where one aims at the full reconstruction of the nal state using a cut-based approach. Recently, this way of reconstructing the t\bar{t}H {o}(H {o}\rightarrow b\bar{b}) process has been found to be extremely challenging. The other analysis is based on a new method employing state-of-the-art jet reconstruction and decomposition techniques where the t\bar{t} pair and the Higgs boson are required to have large transverse momenta and can therefore be reconstructed as massive Higgs and top jets. A recent phenomenological study has shown that the t\bar{t}H {o} process can be recovered as a promising search channel for a low mass Standard Model Higgs boson around 120 GeV using this approach. Finally, to enhance the sensitivity of the t\bar{t}H {o} channel, a combination of the two analyses is presented.
Search For The Higgs Boson In The Vector Boson Fusion Channel At The Atlas Detector
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Author : Eric Ouellette
language : en
Publisher: Springer
Release Date : 2015-01-25
Search For The Higgs Boson In The Vector Boson Fusion Channel At The Atlas Detector written by Eric Ouellette and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-01-25 with Science categories.
This Thesis describes the first measurement of, and constraints on, Higgs boson production in the vector boson fusion mode, where the Higgs decays to b quarks (the most common decay channel), at the LHC. The vector boson fusion mode, in which the Higgs is produced simultaneously with a pair of quark jets, provides an unparalleled opportunity to study the detailed properties of the Higgs, including the possibility of parity and CP violation, as well as its couplings and mass. It thus opens up this new field of study for precision investigation as the LHC increases in energy and intensity, leading the way to this new and exciting arena of precision Higgs research.
Discovery Of The Higgs Boson
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Author : Aleandro Nisati
language : en
Publisher: World Scientific
Release Date : 2016-08-26
Discovery Of The Higgs Boson written by Aleandro Nisati and has been published by World Scientific this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-08-26 with Science categories.
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.