University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 8-2021 A Study of Systematic Uncertainties for a Photon-like Low Energy Excess Search at MicroBooNE Gray Yarbrough [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Elementary Particles and Fields and String Theory Commons, and the Plasma and Beam Physics Commons Recommended Citation Yarbrough, Gray, "A Study of Systematic Uncertainties for a Photon-like Low Energy Excess Search at MicroBooNE. " PhD diss., University of Tennessee, 2021. https://trace.tennessee.edu/utk_graddiss/6575 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Gray Yarbrough entitled "A Study of Systematic Uncertainties for a Photon-like Low Energy Excess Search at MicroBooNE." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Physics. Sowjanya Gollapinni, Major Professor We have read this dissertation and recommend its acceptance: Stefan M Spanier, Nadia Fomin, David C Donovan Accepted for the Council: Dixie L. Thompson Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) A Study of Systematic Uncertainties for a Photon-like Low Energy Excess Search at MicroBooNE A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Gray Yarbrough August 2021 © by Gray Yarbrough, 2021 All Rights Reserved. ii Dedicated to all of those who helped me along the way iii Acknowledgments Thanks to the many people who supported me from University of Tennessee Knoxville. My advisor, Dr. Sowjanya Gollapinni, deserves particular praise for the guidance in introducing me to the MicroBooNE collaboration and her immeasurable support in my dissertation work. Also, particular thanks to my doctoral committee for their support in the dissertation process. Finally, my appreciation is immeasurable to all the professors and staff who supported me at UTK. I would also like to thank the Fermilab and MicroBooNE communities for welcoming me and supporting through my stay at the lab, both in my work and in my life. Finally, thanks to my family for their unwavering support in my career. To my mother and father, the fact that I knew I could always call on you in times of stress was a great comfort. To my grandfather, you could always be relied upon to hear my problems and make me laugh. Thank you all, truly. iv Abstract The premise of this dissertation is the study of and reduction of systematic uncertainties in the MicroBooNE experiment at the Fermi National Accelerator Laboratory. MicroBooNE is a short-baseline oscillation experiment using the innovative liquid argon time projection chamber technology to study, with unprecedented detail, neutrino interactions. The primary goal of MicroBooNE is the investigation of the MiniBooNE low energy excess (LEE) of electron neutrino events, a result which raised fundamental questions on the existence of sterile neutrinos with broad implications to the field of particle physics. The principal study of this dissertation is a study of systematics as part of the LEE search seeking an explanation to the MiniBooNE low energy excess anomaly via neutrino-induced single photon events. A detailed knowledge of uncertainties is necessary to achieve the required precision, and the work presented in this thesis allowed for an estimated three times reduction of systematic uncertainties in the single photon analysis. In addition, a study of beamline properties and systematics on the source beam for MicroBooNE, the Booster Neutrino Beam, with a method of recovering data deemed unfit due to beamline related issues has been performed. Significance of beam-related measurements depends on the protons on target collected and, as such, this result could potentially increase the neutrino data received by MicroBooNE. Overall, these studies have significantly contributed to the precision and confidence of the single photon analysis along with potential for improvements to future analyses in MicroBooNE. v Table of Contents 1 Overview of Thesis1 2 Neutrino Physics4 2.1 Standard Model..................................4 2.2 Neutrino history..................................8 2.3 Neutrino Oscillations...............................9 2.4 Neutrino Interactions............................... 12 2.4.1 Charge Current Quasi-Elastic Interactions............... 15 2.4.2 Deep Inelastic Interactions........................ 15 2.4.3 Resonant Interactions........................... 16 2.4.4 Coherent Interactions........................... 17 2.4.5 Neutrino-Argon Interactions Developement............... 17 2.5 Open Questions in Neutrino Physics...................... 17 2.5.1 Neutrino Mass Hierarchy......................... 18 2.5.2 Absolute Masses of Neutrinos...................... 18 2.5.3 Additional Neutrino States........................ 19 2.5.4 Majorana or Dirac Nature........................ 19 2.5.5 Charge Parity Violation......................... 20 2.6 Neutrino Experiments.............................. 22 2.6.1 Neutrino Accelerator Experiments.................... 23 2.6.2 Long Baseline Experiments....................... 26 2.6.3 Short Baseline Experiments....................... 27 vi 3 The MicroBooNE Experiment 31 3.1 Experimental Motivation............................. 31 3.2 MicroBooNE and Physics Goals......................... 33 3.3 Booster Neutrino Beam.............................. 37 3.3.1 Beam Target and Horn.......................... 38 3.3.2 Booster Neutrino Beam MicroBooNE Era............... 38 3.4 MicroBooNE Construction............................ 39 3.4.1 TPC.................................... 39 3.4.2 Light Collection.............................. 43 3.4.3 Cryogenic System............................. 43 3.4.4 Cosmic Ray Tagger............................ 44 3.4.5 Data Acquisition............................. 44 3.5 MicroBooNE Data Collection.......................... 46 4 MicroBooNE Reconstruction and Simulation 58 4.1 MicroBooNE Simulation............................. 58 4.1.1 Neutrino Flux Simulation........................ 59 4.1.2 Cosmic Generation............................ 59 4.1.3 Neutrino Interactions........................... 60 4.2 MicroBooNE Signal Processing......................... 61 4.2.1 Time Projection Chamber Signals.................... 61 4.2.2 Signal Extraction............................. 63 4.3 Reconstruction.................................. 64 4.3.1 Pandora.................................. 64 4.3.2 Optical Reconstruction.......................... 65 4.3.3 Calorimetry................................ 66 4.3.4 Particle Identification........................... 67 4.3.5 Calibration................................ 68 5 Single Photon Low Energy Excess Search 82 5.1 Goals and Hypothesis............................... 82 vii 5.2 Analysis Overview................................ 83 5.3 Single Photon Selection.............................. 83 5.4 Neutral Current π0 Selection........................... 92 6 Single Photon Systematics 99 6.1 Systematics Frameworks............................. 99 6.1.1 Covariance Matrix Construction..................... 100 6.2 Reweightable Systematic Uncertainties..................... 101 6.2.1 EventWeight Module........................... 101 6.2.2 Input Samples............................... 102 6.2.3 Flux Systematics............................. 103 6.2.4 Cross Section Systematics........................ 105 6.2.5 Total Flux and Cross Section Tables.................. 111 6.2.6 Flux and Cross Section Covariance Matrices.............. 113 6.3 Non-Reweightable Systematics.......................... 113 6.3.1 Detector Systematics Selections..................... 122 6.3.2 Detector Systematics in the Final Selections.............. 122 6.3.3 Photonocuclear Absorption Uncertainties................ 124 6.4 Systematics Constraint and Final Results.................... 128 6.4.1 Estimating the Neutral Current π0 Systematic Constraint....... 128 6.4.2 Hypothesis Testing............................ 137 6.4.3 Fitting to a Neutral Current ∆ Radiative Decay Rate Parameter... 138 7 Booster Neutrino Beam Accelerator Concepts 142 7.1 Accelerator Concept............................... 142 7.2 Fermilab Accelerator Complex.......................... 143 7.2.1 Linear Accelerator............................ 143 7.2.2 Booster.................................. 146 7.2.3 Target and Horn Details......................... 146 7.2.4 Beamline Instrumentation and Devices................. 147 viii 8 Booster Neutrino Beam Systematic Analsysis 149 8.1 Beam Position Study............................... 149 8.1.1 Target Scan Procedure.......................... 150 8.1.2 Figure of Merit Multi-Wire Study.................... 152 8.2 Hadron Production Experiment Data Fitting and BNB Flux Prediction... 163 8.2.1 HARP Data................................ 167 8.2.2 Proton Contribution to Neutrino Flux................. 167 8.2.3 Sanford-Wang Parametrization....................