ATLAS Measurements of the Higgs Boson Coupling to the Top Quark in the Higgs to Diphoton Decay Channel. Doctoral Thesis accepted by University of California, Berkeley, USA

Supervisor’s Foreword
Abstract
Acknowledgments
Contents
1 Introduction
	References
2 Phenomenology
	2.1 Theory of Strong Interactions
		2.1.1 Factorization of Proton–Proton Collisions
	2.2 Theory of Electroweak Interactions
		2.2.1 The Higgs Mechanism
		2.2.2 Fermion Masses and Interactions
	2.3 Higgs Boson Physics
		2.3.1 Production Mechanisms
		2.3.2 Decay Channels
		2.3.3 Coupling Measurement Framework
	2.4 Beyond the Standard Model Higgs
		2.4.1 CP Violation in the Higgs Sector
	References
3 The ATLAS Experiment
	3.1 The Large Hadron Collider
		3.1.1 Luminosity
	3.2 The ATLAS Detector
		3.2.1 Inner Detector
		3.2.2 Calorimeters
		3.2.3 Muon Spectrometer
		3.2.4 Trigger
	References
4 Object Reconstruction
	4.1 Tracks and Vertices
	4.2 Photons
		4.2.1 Photon Identification
		4.2.2 Photon Isolation
		4.2.3 Primary Vertex Selection in Diphoton Events
	4.3 Electrons
		4.3.1 Electron Identification
		4.3.2 Electron Isolation
	4.4 Muons
		4.4.1 Muon Identification
		4.4.2 Muon Isolation
	4.5 Hadronic Jets
		4.5.1 Flavor Tagging
	4.6 Missing Transverse Energy
	References
5 Data and Monte Carlo Samples
	5.1 Data: LHC Run 2
		5.1.1 Data Control Samples
	5.2 Simulated Samples
		5.2.1 SM Higgs Boson Samples
		5.2.2 BSM Higgs Samples
		5.2.3 Background Samples
	References
6 Statistical Model
	6.1 Motivation for Categorization
		6.1.1 A Short Proof
	6.2 Signal and Background Shapes
		6.2.1 Signal Model
		6.2.2 Background Model
	6.3 Likelihood Model
		6.3.1 Treatment of Systematics
		6.3.2 Generation of Asimov Datasets
	6.4 Sources of Systematic Uncertainty
		6.4.1 Theoretical Uncertainties
		6.4.2 Experimental Uncertainties
	6.5 Weighting Data for Presentation
	References
7 Machine Learning Techniques
	7.1 Multivariate Analysis
		7.1.1 Classification
	7.2 Boosted Decision Trees
		7.2.1 Boosting
		7.2.2 Multiclass BDT
	7.3 Hyper-Parameter Optimization
		7.3.1 Grid Scan
		7.3.2 Gaussian Processes Minimization
	References
8 Reconstruction of Top Decays
	8.1 Reconstruction Strategy
		8.1.1 Hadronic Channel
		8.1.2 Leptonic Channel
	8.2 Training of the Top Reco BDT
		8.2.1 Constructing Signal and Background Samples
		8.2.2 Training Variables
	8.3 Performance
		8.3.1 Hadronic Channel
		8.3.2 Leptonic Channel
	References
9 Selection of tbartH(γγ) Events
	9.1 Poisson Number-Counting Significance
	9.2 Categorization of Events
		9.2.1 Hadronic Channel
		9.2.2 Leptonic Channel
	9.3 Decomposition of Continuum Background
		9.3.1 Hadronic Channel
		9.3.2 Leptonic Channel
	References
10 First Observation of tbartH Production
	10.1 Combination of Higgs Decay Channels
		10.1.1 Input Analyses
		10.1.2 Systematic Uncertainties
		10.1.3 Results of Combined Analysis
	10.2 tbartH in the Diphoton Decay Channel
		10.2.1 Signal and Background Shapes
		10.2.2 Systematic Uncertainties
		10.2.3 Results
	References
11 CP-Sensitive Categorization  of tbartH(γγ) Events
	11.1 Number-Counting Limit on CP Mixing
	11.2 Sensitive Observables
	11.3 Multivariate Categorization Strategy
		11.3.1 Hadronic Channel
		11.3.2 Leptonic Channel
	11.4 Determination of Category Boundaries
	References
12 Measurement of CP Properties in tbartH and tH
	12.1 Treatment of Loop Processes
		12.1.1 Kinematics of Gluon Fusion
		12.1.2 Effective Loop Couplings
	12.2 Signal and Background Model
		12.2.1 Signal and Background Shapes
		12.2.2 Signal Yield Dependence on Mixing Angle
	12.3 Systematic Uncertainties
	12.4 Results
		12.4.1 Sensitivity to SM tbartH and tH
		12.4.2 Constraints on CP Mixing
	References
13 Higgs Couplings in Hrightarrowγγ
	13.1 Event Categorization
		13.1.1 Leptonic VH
		13.1.2 Vector Boson Fusion and Hadronic VH
		13.1.3 Gluon Fusion
	13.2 Signal and Background
	13.3 Systematic Uncertainties
	13.4 Results (79.8 fb-1)
		13.4.1 Higgs Cross Section by Production Mode
		13.4.2 Measurement of STXS
	References
14 Conclusions
	References
Appendix A Search for TeV-Scale Gravity
Appendix B Multijet Modeling with MG5_aMC@NLO
Appendix C Radiation Damage in the IBL
C.1  Single Event Upset
C.2  Measurement of Leakage Current