Measurement of the Top Quark Mass in the Dilepton Final State Using the Matrix Element Method (eBook)

Supervisor’s Foreword 6
Contents 8
Introduction 11
References 13
Experimental Environment 15
2.1 The Tevatron Accelerator Complex 15
2.2 The DØ Experiment 17
2.2.1 The Coordinate System 18
2.2.2 The Tracking System 18
2.2.3 The Calorimeter 20
2.2.4 The Muon Spectrometer 21
2.2.5 The Luminosity Monitors 23
2.2.6 The Trigger System and Data Acquisition 24
References 26
Event Reconstruction and Simulation 27
3.1 Tracks 27
3.2 Vertices 28
3.2.1 Primary Vertex 28
3.2.2 Secondary Vertex 28
3.3 Electrons 28
3.4 Muons 29
3.5 Calibration of Charged Leptons 30
3.6 Jets 31
3.7 Jet Energy Scale 32
3.7.1 Overall Jet Energy Scale 32
3.7.2 Bottom Quark Jet Energy Scale 37
3.7.3 Jet Energy Resolution 39
3.8 Missing Transverse Energy = E 39
3.9 Data Quality 39
3.10 Monte Carlo Simulation 40
References 40
The Top Quark and the Concept of Mass 42
4.1 The Top Quark within the Standard Model 42
4.2 Top Quark Production 44
4.3 Top Quark Decay 46
4.3.1 Dilepton Channel 47
4.3.2 Lepton + Jets Channel 48
4.3.3 Alljets Channel 48
4.4 The Concept of Mass 48
4.5 Relevance of the Top Quark Mass 49
4.6 Measurement Methods of the Top Quark Mass 50
4.6.1 Indirect Constraints 51
4.6.2 Reconstruction of Decay Products 51
4.6.3 Measurements of the t t Cross Section 51
References 52
The Matrix Element Method 54
5.1 Event Likelihood 54
5.2 Process Likelihood 55
5.3 Description of the Detector Response 56
5.3.1 Parameterization of the Jet Energy Resolution 59
5.3.2 Parameterization of the Muon Momentum Resolution 67
5.3.3 Parameterization of the s Lepton Decay 69
5.4 Parameterization of the Top Pair Transverse Momentum 71
5.5 Calculation of the Signal Likelihood 73
5.6 Normalization of the Signal Likelihood 76
5.7 Calculation of the Background Likelihood 77
5.8 Normalization and Performance of the Background Likelihood 79
5.9 Likelihood Evaluation 79
5.10 Ensemble Testing 81
References 83
Measurement of the Top Quark Mass 85
6.1 Data Samples and Event Selection 85
6.2 Parton-Level Studies 89
6.2.1 Monte Carlo Samples 94
6.2.2 Normalization 95
6.2.3 Signal-Only Studies 96
6.2.4 Studies Including (Z ss) jj and ( Z ss) bb Events 98
6.2.5 Studies Including (Z ss) jj and WWjj Events 101
6.2.6 Measurement of the Signal Fraction 105
6.3 Calibration of the Method 105
6.3.1 Monte Carlo Samples 107
6.3.2 Normalization 108
6.3.3 Validation of the Integration over the Top Pair Transverse Momentum 109
6.3.4 Calibration for Run IIa and Run IIb 110
6.4 Measurement 113
6.5 Systematic Uncertainties 115
6.5.1 Detector Modeling 116
6.5.2 Physics Modeling 118
6.5.3 Uncertainties from the Measurement Method 120
6.5.4 Summary of Systematic Uncertainties 121
6.6 Combination of the Run IIa and Run IIb Mass Measurements 121
6.6.1 The Best Linear Unbiased Method 121
6.6.2 Combination 123
References 125
Improved Mass Measurement 127
7.1 Motivation 127
7.2 Modifications 128
7.2.1 Event Likelihoods 129
7.2.2 Normalization of the Jet Transfer Functions 129
7.2.3 Likelihood Evaluation 130
7.3 Parton-Level Studies 131
7.3.1 Monte Carlo Samples 131
7.3.2 Normalization 131
7.3.3 Signal-Only Studies 131
7.3.4 Studies Including (Z ss) jj and ( Z ss) bb Events 136
7.3.5 Studies Including (Z ss) jj and WWjj Events 143
References 143
Conclusion 144
8.1 Summary and Interpretation 144
8.2 Outlook 147
References 148
Appendices 150
A: Solving for the Event Kinematics 150
B: The Jacobian Determinant for the Signal Integration 152
Reference 155