Purdue University Purdue e-Pubs Open Access Dissertations Theses and Dissertations 12-2016 The search for dark matter in xenon: Innovative calibration strategies and novel search channels Shayne Edward Reichard Purdue University Follow this and additional works at: https://docs.lib.purdue.edu/open_access_dissertations Part of the Physics Commons Recommended Citation Reichard, Shayne Edward, "The es arch for dark matter in xenon: Innovative calibration strategies and novel search channels" (2016). Open Access Dissertations. 994. https://docs.lib.purdue.edu/open_access_dissertations/994 This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for additional information. Graduate School Form 30 Updated PURDUE UNIVERSITY GRADUATE SCHOOL Thesis/Dissertation Acceptance This is to certify that the thesis/dissertation prepared By Shayne Edward Reichard Entitled THE SEARCH FOR DARK MATTER IN XENON: INNOVATIVE CALIBRATION STRATEGIES AND NOVEL SEARCH CHANNELS For the degree of Doctor of Philosophy Is approved by the final examining committee: Rafael F. Lang Chair Dimitrios Giannios Matthew Jones Matthew L. Lister To the best of my knowledge and as understood by the student in the Thesis/Dissertation Agreement, Publication Delay, and Certification Disclaimer (Graduate School Form 32), this thesis/dissertation adheres to the provisions of Purdue University’s “Policy of Integrity in Research” and the use of copyright material. Approved by Major Professor(s): Rafael F. Lang Approved by: John P. Finley 11/21/2016 Head of the Departmental Graduate Program Date THE SEARCH FOR DARK MATTER IN XENON: INNOVATIVE CALIBRATION STRATEGIES AND NOVEL SEARCH CHANNELS A Dissertation Submitted to the Faculty of Purdue University by Shayne Edward Reichard In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy December 2016 Purdue University West Lafayette, Indiana ii TABLE OF CONTENTS Page LIST OF TABLES ::::::::::::::::::::::::::::::::: v LIST OF FIGURES :::::::::::::::::::::::::::::::: vii ABSTRACT :::::::::::::::::::::::::::::::::::: xiv 1 DARK MATTER :::::::::::::::::::::::::::::::: 1 1.1 The Friedmann Equation ::::::::::::::::::::::::: 2 1.2 Big Bang Nucleosynthesis :::::::::::::::::::::::: 6 1.3 The Cosmic Microwave Background ::::::::::::::::::: 9 1.3.1 The Curvature of the Universe :::::::::::::::::: 13 1.3.2 Baryon Density :::::::::::::::::::::::::: 13 1.3.3 Dark Matter Density ::::::::::::::::::::::: 13 1.4 Galaxies :::::::::::::::::::::::::::::::::: 14 1.4.1 Milky Way Galaxy :::::::::::::::::::::::: 14 1.4.2 Other Spiral Galaxies ::::::::::::::::::::::: 15 1.4.3 Elliptical Galaxies :::::::::::::::::::::::: 16 1.5 Galaxy Clusters :::::::::::::::::::::::::::::: 17 1.5.1 Orbits of Galaxies ::::::::::::::::::::::::: 18 1.5.2 Hot Gas :::::::::::::::::::::::::::::: 18 1.5.3 Gravitational Lensing ::::::::::::::::::::::: 19 1.6 Structure Formation ::::::::::::::::::::::::::: 21 1.7 Large-Scale Structures :::::::::::::::::::::::::: 23 1.8 Dark Matter Candidates ::::::::::::::::::::::::: 25 1.8.1 Weakly Interacting Massive Particle ::::::::::::::: 26 1.8.2 Axion ::::::::::::::::::::::::::::::: 28 2 DETECTION OF DARK MATTER ::::::::::::::::::::: 31 2.1 Collider Experiments ::::::::::::::::::::::::::: 31 2.2 Indirect Detection ::::::::::::::::::::::::::::: 33 2.3 Direct Detection ::::::::::::::::::::::::::::: 34 2.3.1 Differential Energy Spectrum :::::::::::::::::: 35 2.3.2 Dark Matter Halo Density :::::::::::::::::::: 36 2.3.3 Velocity Distribution ::::::::::::::::::::::: 37 2.3.4 Nuclear Form Factor ::::::::::::::::::::::: 38 2.3.5 Interaction Factor ::::::::::::::::::::::::: 41 2.3.6 Energy Detection Efficiency ::::::::::::::::::: 42 iii Page 2.3.7 Energy Resolution and Threshold :::::::::::::::: 43 2.3.8 Target Mass Fraction ::::::::::::::::::::::: 44 2.3.9 Annual Modulation :::::::::::::::::::::::: 44 2.3.10 WIMP Event Rate :::::::::::::::::::::::: 45 2.4 Low-Background Requirements ::::::::::::::::::::: 48 3 SCATTERING EXPERIMENTS ::::::::::::::::::::::: 51 3.1 Liquid Noble Element Detectors ::::::::::::::::::::: 52 3.1.1 WIMP Recoil Sensitivity ::::::::::::::::::::: 52 3.1.2 Scintillation Signal :::::::::::::::::::::::: 53 3.1.3 Ionization Signal ::::::::::::::::::::::::: 55 3.1.4 Electroluminescence ::::::::::::::::::::::: 56 3.1.5 Radiopurity :::::::::::::::::::::::::::: 57 3.1.6 Self-Shielding ::::::::::::::::::::::::::: 57 3.1.7 Scalability ::::::::::::::::::::::::::::: 59 3.1.8 Discrimination :::::::::::::::::::::::::: 59 3.2 Cryogenic Detectors ::::::::::::::::::::::::::: 60 3.2.1 Low-Temperature Phonon Signal :::::::::::::::: 60 3.2.2 Ionization Collection ::::::::::::::::::::::: 62 3.3 Solid Scintillators ::::::::::::::::::::::::::::: 63 4 XENON ::::::::::::::::::::::::::::::::::::: 65 4.1 The Principle of a Dual-Phase Time Projection Chamber ::::::: 65 4.2 Calibration :::::::::::::::::::::::::::::::: 67 4.3 Light Collection Efficiency :::::::::::::::::::::::: 68 4.4 Energy Scales ::::::::::::::::::::::::::::::: 70 4.4.1 Electronic Recoil Equivalent Energy ::::::::::::::: 70 4.4.2 Nuclear Recoil Equivalent Energy :::::::::::::::: 70 4.4.3 Combined Energy Scale ::::::::::::::::::::: 71 5 RESULTS FROM A CALIBRATION OF XENON100 USING A DISSOLVED RADON-220 SOURCE ::::::::::::::::::::::::::::: 73 5.1 The XENON100 Detector in Run 14 :::::::::::::::::: 74 5.2 220Rn Decay Chain and Observed Time Evolution ::::::::::: 75 5.3 Contamination from the Veto :::::::::::::::::::::: 78 5.4 Combined Leakage Rate ::::::::::::::::::::::::: 80 5.5 Alpha Spectroscopy :::::::::::::::::::::::::::: 81 5.6 220Rn-216Po Coincidence and Convection :::::::::::::::: 83 5.7 The half-life of 212Po ::::::::::::::::::::::::::: 87 5.8 Low-Energy Calibration ::::::::::::::::::::::::: 90 5.9 Conclusions :::::::::::::::::::::::::::::::: 94 6 DARK MATTER SCATTERING INELASTICALLY OFF XENON NUCLEI 95 6.1 Nuclear Structure and WIMP-Nucleon Currents :::::::::::: 96 iv Page 6.2 Structure Factors ::::::::::::::::::::::::::::: 97 6.3 Kinematics of Inelastic Scattering :::::::::::::::::::: 102 6.4 Signatures of Inelastic Dark Matter Scattering ::::::::::::: 105 6.5 Implications for Dark Matter Searches ::::::::::::::::: 111 6.6 Conclusions :::::::::::::::::::::::::::::::: 114 7 SUPERNOVA NEUTRINO PHYSICS WITH XENON DARK MATTER DE- TECTORS: A TIMELY PERSPECTIVE ::::::::::::::::::: 115 7.1 Supernova Neutrino Emission :::::::::::::::::::::: 117 7.1.1 Supernova Neutrino Emission Properties :::::::::::: 118 7.1.2 Neutrino Flavor Conversion ::::::::::::::::::: 121 7.2 Supernova Neutrino Scattering with Dual-Phase Xenon Detectors :: 122 7.2.1 Scattering Rates in Terms of Recoil Energy :::::::::: 124 7.2.2 Generation of the Observable S1 and S2 Signals :::::::: 127 7.2.3 Observable Scattering Rates :::::::::::::::::: 130 7.3 S2-Only Analysis ::::::::::::::::::::::::::::: 133 7.4 Supernova Neutrino Detection :::::::::::::::::::::: 135 7.4.1 Detection Significance :::::::::::::::::::::: 136 7.4.2 Distinguishing Between Supernova Progenitors ::::::::: 138 7.4.3 Reconstructing the Supernova Neutrino Light Curve :::::: 138 7.4.4 Neutrino Differential Flux :::::::::::::::::::: 141 7.4.5 Total Energy Emitted into Neutrinos :::::::::::::: 144 7.4.6 Comparison with Dedicated Neutrino Detectors :::::::: 147 7.4.7 SNEWS & False Alarms ::::::::::::::::::::: 148 7.5 Experimental Factors ::::::::::::::::::::::::::: 150 7.5.1 Signal Uncertainty from Qy ::::::::::::::::::: 150 7.5.2 Sources of Increased Background Rates ::::::::::::: 153 7.5.3 Sensitivity Limitation from Event Pile-Up ::::::::::: 154 7.6 Conclusions :::::::::::::::::::::::::::::::: 155 A Calculations of Velocity Distribution ::::::::::::::::::::: 159 B Calculations of Event Rates :::::::::::::::::::::::::: 161 C Convection Parameter ::::::::::::::::::::::::::::: 163 LIST OF REFERENCES ::::::::::::::::::::::::::::: 165 VITA :::::::::::::::::::::::::::::::::::::::: 180 v LIST OF TABLES Table Page 5.1 The results of a GEANT4 Monte Carlo simulation of leakage events from long-lived isotopes in the veto (buffer) region. The intensities, deposition probabilities, and overall contribution per mille are given for each gamma. The values correspond to the entire active region. :::::::::::: 79 5.2 The total leakage contribution from 208Tl is determined according to the different combinations of de-excitation gammas. The intensities, deposition probabilities, and overall contribution per mille are given for each decay path. The final leakage value accounts for the 36% branching of 208Tl. :: 79 5.3 Q-values, scintillation values (means and widths at 400 V=cm), and calcu- lated light yields of each alpha decay in Figure 5.4. :::::::::::: 83 5.4 The results of a GEANT4 Monte Carlo simulation of leakage events from long-lived isotopes in the veto (buffer) region. The intensities, deposition probabilities, and overall contribution per mille are given for each gamma. The values correspond to the entire active region. :::::::::::: 93 5.5 The total leakage contribution from 208Tl is determined according to the different combinations of de-excitation gammas. The intensities, deposition probabilities, and overall contribution per mille are given for each decay path. The final leakage value accounts for the 36% branching of 208Tl. : 93 6.1 Minimal and maximal recoil energies, in keV, between which inelastic scat- tering is allowed (see Eq. (6.13)) for the two xenon isotopes and various WIMP masses. :::::::::::::::::::::::::::::::: 103 6.2 Minimum energy Evis in keV above