A Search for Exotic Higgs Decays: Or: How I Learned to Stop Worrying and Love Long-Lived Particles (Springer Theses) 9783031304651, 9783031304668, 3031304659

The absence of new physics at the TeV scale observed thus far at the Large Hadron Collider (LHC) motivates an increasing

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Table of contents :
Supervisor’s Foreword
Abstract
Preface
References
Acknowledgements
Contents
Part I Theoretical Motivation
1 The Standard Model
1.1 Quantum Field Theory and Gauge Theory
1.1.1 Cross Sections and Decay Widths
1.1.2 Symmetries and Representations
1.2 Quantum Electrodynamics
1.3 Quantum Chromodynamics
1.4 Electroweak Unification
1.4.1 The Weak Force
1.4.2 Glashow-Weinberg-Salam Theory
1.4.3 Symmetry Breaking and the Higgs Mechanism
1.5 The Higgs Boson
1.6 Summary
1.6.1 Shortcomings of the Standard Model
References
2 Physics Beyond the Standard Model
2.1 Supersymmetry
2.2 Models of Uncolored Naturalness
2.2.1 Folded SUSY
2.2.2 Twin Higgs
2.2.3 Quirky Little Higgs
2.3 Neutral Naturalness Phenomenology
2.3.1 Exotic Higgs Decays
2.3.2 Glueball Decays
2.4 Long-Lived Particles
2.5 Bottom-up Considerations
2.5.1 The Hidden Sector
2.5.2 A Simplified Model
2.6 Existing Constraints on Br(Hrightarrowss)
References
Part II Experimental Apparatus
3 The Large Hadron Collider and the ATLAS Detector
3.1 The Large Hadron Collider
3.1.1 Machine Design
3.1.2 Performance and Operation
3.2 The ATLAS Detector
3.2.1 The Inner Detector
3.2.2 Calorimeter
3.2.3 The Muon Spectrometer
3.2.4 Trigger
References
4 Event Reconstruction
4.1 Track and Vertex Reconstruction
4.1.1 Track Reconstruction
4.1.2 Primary Vertex Reconstruction
4.2 Physics Object Reconstruction
4.2.1 Jets
4.2.2 Muons
4.2.3 Electrons
4.2.4 Photons
References
5 Reconstruction of Long-Lived Particle Decays
5.1 Large Radius Tracking
5.1.1 LRT Performance
5.2 Displaced Vertex Reconstruction
5.2.1 Description of the Algorithm
5.2.2 Performance
References
Part III Search for Exotic Higgs Decays
6 Data and Simulated Samples
6.1 Simulation
6.1.1 Monte-Carlo Event Generation
6.1.2 Simulation of Higgs Boson Decays to Long-Lived Particles
6.1.3 Simulation of Z+jets Events
6.2 Data
6.2.1 Trigger
6.2.2 The RPVLL Stream
References
7 Search for Higgs Decays to Long-Lived Particles
7.1 Event Selection
7.1.1 Preselection
7.1.2 Displaced Vertex Selection
7.1.3 Event Categorization
7.1.4 Analysis Cutflow
7.2 Background Estimation
7.2.1 Closure Test
7.2.2 Validation
7.2.3 Signal Injection Test
7.3 Signal Systematic Uncertainties
7.3.1 Uncertainties on Standard Objects
7.3.2 Uncertainties on Non-standard Reconstruction
7.3.3 Theory and Signal Modeling
7.3.4 Other Sources of Systematic Error
7.3.5 Summary of Uncertainties
References
8 Results
8.1 Unblinded Results
8.2 Statistics
8.2.1 The Likelihood Function
8.2.2 Hypothesis Tests
8.2.3 Confidence Intervals and the CLs Method
8.3 Exclusion Limits on B(Hrightarrowaarightarrowboverlinebboverlineb)
8.3.1 Lifetime Reweighting
8.3.2 Limits
8.3.3 Better than Zero?
8.3.4 Summary of Results
References
9 Conclusion
References

A Search for Exotic Higgs Decays: Or: How I Learned to Stop Worrying and Love Long-Lived Particles (Springer Theses)
 9783031304651, 9783031304668, 3031304659

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