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Measurements of the W-pair production rate and the W mass using four-jet
events at LEP
van Dierendonck, D.N.
Publication date
2002
Link to publication
Citation for published version (APA):
van Dierendonck, D. N. (2002). Measurements of the W-pair production rate and the W mass
using four-jet events at LEP.
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Contents s
11 Introduction 1 22 Theory 3
2.11 Weak Interactions and the Standard Model 3
2.22 W-Pair Production in e+e~ collisions 10
2 33 W Decay 12 2.44 Four-Fermion Production 14
2.55 Theoretical Uncertainties 18 2.5.11 Radiative Corrections 19 2.5.22 Fragmentation and Hadronization 20
2.5.33 Bose-Einstein Correlations 23 2.5.44 Color Reconnection 23
33 Tools 25
3.11 LEP 25 3.1.11 LEP Beam Energy Determination 26
3.22 The L3 Detector 27 3.33 Monte Carlo Simulation 35
3.3.11 Event Generators 35 3.3.22 Detector Simulation 38
44 Event Reconstruction 41
4.11 Track Reconstruction 41 4.22 Cluster Formation in the Calorimeters 42
4.33 Energy Determination 42 4.3.11 Related Analysis Variables 45
4.44 Jet Reconstruction 46 4.4.11 Related Analysis Variables 46
4.55 Constrained Fitting 47 4.5.11 Related Analysis Variables 49
CONTENTS S
55 Event Selection and Cross Section Results 53
5.11 Introduction 53 5.22 Selection 55 5.33 Neural Network 58
5.3.11 Training the Neural Network 61 5.44 Results and Cross Section Determination 63
5.4.11 Fitting Method 64 5.4.22 Results 66 5.55 Systematic Error Analysis 66
5.5.11 Modeling of the Detector Response 68
5.5.22 Luminosity Determination 70 5.5.33 Modeling of the W+W" Signal 71 5.5.44 Modeling of the Backgrounds 75 5.5.55 Systematic Error Summary 78 5.66 W Mass from WW Cross Section 79
66 Direct W Mass Measurement 83
6.11 Fit Method 83 6.22 Jet Pairing 85 6.33 Monte Carlo Statistics 86
6.44 Implementation and Technical Checks 88 6.55 Results and Systematic Error Analysis 88
6.5.11 Detector Response Uncertainties 91 6.5.22 Signal and Background Modeling 93
6.5.33 Fragmentation 95 6.5.44 Final State Interactions 96 6.5.55 LEP Energy Uncertainty 101
6.5.66 Summary 102 6.66 Combination 102
77 Discussion 103
7.11 Cross Section 103 7.1.11 Anomalous Couplings 103
7.1.22 W Branching Fractions and the CKM Matrix 107
7.1.33 Invisible W Decays 109 7.1.44 Large Extra Dimensions 112
7.22 WMass 115 7.2.11 Consistency of W Mass Measurements 115
7.2.22 Constraints on the Higgs Mass 117 7.2.33 Possible Improvements on the Measurement 118
CONTENTS S 7.2.44 Future Prospects 121 Bibliographyy 123 Summaryy 135 Samenvattingg 139 Acknowledgementss 141 ui i
