Search for Exotic Higgs Boson Decays to Merged Diphotons. A Novel CMS Analysis Using End-to-End Deep Learning. Doctoral Thesis accepted by Carnegie Mellon University, Pittsburgh, USA

Description

Supervisor’s Foreword Abstract Acknowledgments Contents 1 Introduction References 2 The LHC and the CMS Detector 2.1 The LHC 2.2 Particle Interactions with Matter 2.3 The CMS Detector 2.3.1 Inner Tracking 2.3.2 Calorimeters 2.3.3 Magnet System 2.3.4 Outer Tracking 2.4 The CMS Trigger System 2.4.1 L1 Trigger 2.4.2 HLT Trigger 2.5 Physics Object Reconstruction 2.5.1 PF Elements 2.5.2 PF Objects 2.6 Detector Simulation References 3 Theory and Phenomenology 3.1 The Standard Model 3.1.1 QED 3.1.2 QCD 3.1.3 Weak Interactions 3.1.4 Higgs Sector 3.2 Challenges with the SM 3.3 The Extended Higgs Sector 3.3.1 Hrightarrowaa rightarrow4γ Phenomenology References 4 Analysis Strategy 4.1 End-to-End Particle Reconstruction 4.2 H -> aa -> 4g Discrimination 4.3 Analysis Strategy References 5 Data Sets 5.1 Recorded Data 5.2 Simulated Data 5.2.1 Signal Samples 5.2.2 Background Samples References 6 Signal Selection 6.1 Trigger 6.2 Photon Preselection 6.3 a -> gg Identification 6.4 Event Selection 6.5 Event Yields References 7 arightarrowγγ Mass Regression 7.1 Image Construction 7.2 Training 7.3 Validation 7.4 Benchmarking 7.4.1 a -> gg in Simulated H -> aa -> 4g 7.4.2 pi0 -> gg in Data 7.5 Robustness of the Algorithm 7.5.1 pi0 -> gg in Data 7.5.2 Z -> ee Electrons in Data 7.5.3 Z Z -> ee Electrons in Data Versus Simulation 7.5.4 a -> gg in Simulated H -> aa -> fg References 8 Analysis 8.1 Signal Model 8.1.1 Photon Identification Scale Factors 8.1.2 HLT Trigger Scale Factors 8.1.3 Pileup Re-weighting 8.1.4 Sample Interpolation 8.2 Background Model 8.2.1 QCD Jet Substructure 8.2.2 Background Estimation 8.2.3 Background Validation 8.3 Systematics 8.3.1 pT Re-weighting 8.3.2 Background Parametrization 8.3.3 H -> gg Template Fraction 8.3.4 Luminosity Uncertainty 8.3.5 Photon ID Scale Factor Uncertainty 8.3.6 HLT Trigger Scale Factor Uncertainty 8.3.7 mGamma Regressor Scale and Smearing 8.3.8 Summary References 9 Results 9.1 Expected Sensitivity 9.1.1 Maximum Likelihood Estimation (MLE) 9.1.2 Impacts 9.1.3 Control Region Signal Extraction Tests 9.1.4 N-1 Expected Upper Limits 9.1.5 Expected Upper Limits 9.2 Observed Results 9.2.1 Impacts 9.2.2 Goodness-of-fit 9.2.3 Observed 2D-mGamma Distribution 9.2.4 Observed Upper Limits 9.2.5 Discussion References 10 Conclusions References Appendix Supplementary Studies A.1 mGamma spectrum of QCD jets A.2 Minimally Processed Versus Clustered Data Reference