Neutrino Physics in Present and Future Kamioka Water‐Čerenkov Detectors with Neutron Tagging

"This book discusses the upgrade of the Super-Kamiokande (SK) detector, which consists in the addition of a salt of gadolinium into the detector's water, the goal being to endow it with a very high-efficiency ability to detect neutrons: the SuperK-Gd project. This will substantially improve the scientific value of the SK detector because, among others, neutron production is related to the matter-antimatter character of the interacting neutrino. In this book the authors develop several procedures for maximizing the impact of neutron tagging in various physics analyses involving a broad range of neutrino energy. They thoroughly study the impact of new backgrounds introduced by Gd in key physics analyses, most remarkably including the search for the Diffuse Supernova Neutrino Background. At GeV energies, the neutron tagging improvements are evaluated by performing a complete neutrino oscillation sensitivity study using atmospheric and long baseline neutrinos, with a focus on the neutrino mass hierarchy and the leptonic CP violation. In order to prove the relevance of neutron tagging with the available data, the authors apply the neutron-tagging tools developed here to the 4th phase of the SK detector, which is already capable of detecting a low fraction of the neutrons produced through hydrogen-neutron captures. A global oscillation analysis of the SK's atmospheric neutrino data is also conducted."-- Provided by publisher Supervisor’s Foreword 7 Abstract 10 Acknowledgements 12 Contents 14 1 Introduction 18 References 21 2 Introduction to Neutrino Physiscs 22 2.1 Main Neutrino Sources 22 2.1.1 Atmospheric Neutrinos 23 2.1.2 Accelerator Neutrinos 24 2.1.3 Solar Neutrinos 25 2.1.4 Reactor Neutrinos 26 2.2 Supernova Neutrinos 27 2.2.1 Supernova Burst 27 2.2.2 Diffuse Supernova Neutrino Background 30 2.3 Neutrino Mass and Neutrino Oscillations 31 2.3.1 Neutrino Masses 31 2.3.2 Neutrino Oscillations 34 2.3.3 Experimental Status 40 2.4 Neutrino-Nucleus Interactions 40 References 45 3 The Super-Kamiokande Detector 48 3.1 Detector Overview 48 3.2 Čerenkov Radiation 49 3.3 Detector Description 52 3.3.1 Water Tank 52 3.3.2 Photomultipliers 52 3.4 Water and Air Purification Systems 55 3.5 SK-IV Electronics and Data Acquisition 57 3.6 Calibration of the Detector 58 References 58 4 The SuperK-Gd Project 60 4.1 Gadolinium-Neutron Tagging 60 4.2 Gadolinium Addition to Super-Kamiokande 62 4.3 Main Physics Outcomes 64 4.3.1 Low Energy 64 4.3.2 High Energy 65 4.4 EGADS R&D Program and Experiment 66 4.4.1 Detector Description 66 4.4.2 Water Purification System 66 4.4.3 Data Acquisition System 68 4.4.4 PMT Pre-Calibration 68 4.4.5 Detector Construction and Instrumentation 70 4.4.6 Monitoring and Main Results of the EGADS Program 71 References 77 5 On Relevant Items for SuperK-Gd Physics 78 5.1 Neutron Production in Neutrino-Nucleus Interactions 78 5.2 Gd-Neutron Tagging Reconstruction 81 5.2.1 Monte Carlo Simulation 81 5.2.2 Neutron Tagging Algorithm 85 5.2.3 Overall Gd-Neutron Tagging Efficiency 98 5.3 Classification of Charged Current and Neutral Current Interactions 99 5.4 Neutrino-Antineutrino Separation 102 5.5 Neutron-Corrected Reconstructed Neutrino Energy 105 5.6 Radioactive Contamination 106 5.6.1 Measurement of Radioactive Contamination in Materials with HPGe Germanium Detectors: Gadolinium Sulphate 107 5.6.2 238U Spontaneous Fission 112 5.6.3 Radioactivity-Induced Neutron Production 113 5.6.4 β-Rays from Radioactivity 115 References 117 6 SuperK-Gd Physics Potential 118 6.1 Reactor Neutrinos 118 6.2 Diffuse Supernova Neutrino Background 121 6.3 Silicon Burning Stage 122 6.4 Supernova Burst 123 6.5 Solar Neutrinos 124 6.6 Atmospheric Neutrinos 126 6.6.1 Monte Carlo Simulation, Event Classification and Reconstruction in Super-Kamiokande 126 6.6.2 Neutral Current and Charged Current Separation for Fully Contained Samples 140 6.6.3 Neutrino and Antineutrino Separation for Fully Contained Samples 143 6.6.4 Neutron-Corrected Reconstructed Neutrino Energy for Fully Contained Samples 152 6.6.5 Oscillation Analysis Sensitivity 158 6.7 Long-Baseline Neutrinos 161 6.7.1 The T2K Experiment 164 6.7.2 Monte Carlo Simulation and Gd-Neutron Tagging 166 6.7.3 T2K Neutrino Event Selection 166 6.7.4 Neutrino-Antineutrino Separation 166 6.7.5 Neutron-Corrected Reconstructed Neutrino Energy 170 6.7.6 Oscillation Analysis 172 6.8 The Next Generation: Physics Potential of Gd-Doping in Hyper-Kamiokande 175 6.8.1 Detector Description 176 6.8.2 Atmospheric Neutrinos 178 6.8.3 Long Baseline Neutrinos 179 References 184 7 Neutron-Tagging with Hydrogen in Super-Kamiokande IV: Global Atmospheric Neutrino Oscillation Analysis with SK 185 7.1 Hydrogen-Neutron Tagging 185 7.1.1 H-Neutron Tagging Analysis 186 7.2 Including Neutron-Tagging Information in SK Atmospheric Neutrino Data Analysis 188 7.2.1 Neutral Current and Charged Current Separation for Fully Contained Samples 190 7.2.2 Neutrino and Antineutrino Separation for Fully Contained Samples 194 7.2.3 Neutron-Corrected Reconstructed Neutrino Energy for Fully Contained Samples 209 7.3 Oscillation Analysis 212 7.3.1 Systematic Errors 212 7.3.2 Oscillation Sensitivity Study 227 7.3.3 Data Fit Results 232 References 236 8 Conclusions 238 Appendix A Evaluation of Systematic Errors in the Neutrino Oscillation Analyses with SuperK-Gd 240 Appendix B Evaluation of Systematic Errors in the Neutrino Oscillation Analyses with Hyper-Kamiokande 246 Appendix C Neutron-Corrected Energy for Fully Contained Events in Super-Kamiokande with H-Neutron Tagging 252 Appendix D Systematic Errors at Best Fit Point in the Global Atmospheric Neutrino Oscillation Analysis with H-neutron Tagging in SK 257 Curriculum Vitae 259 Front Matter ....Pages i-xviii Introduction (Pablo Fernández Menéndez)....Pages 1-4 Introduction to Neutrino Physiscs (Pablo Fernández Menéndez)....Pages 5-30 The Super-Kamiokande Detector (Pablo Fernández Menéndez)....Pages 31-42 The SuperK-Gd Project (Pablo Fernández Menéndez)....Pages 43-60 On Relevant Items for SuperK-Gd Physics (Pablo Fernández Menéndez)....Pages 61-100 SuperK-Gd Physics Potential (Pablo Fernández Menéndez)....Pages 101-167 Neutron-Tagging with Hydrogen in Super-Kamiokande IV: Global Atmospheric Neutrino Oscillation Analysis with SK (Pablo Fernández Menéndez)....Pages 169-221 Conclusions (Pablo Fernández Menéndez)....Pages 223-224 Back Matter ....Pages 225-247