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Measurement of Neutrino Electron Scattering and Inverse Beta-Decay of Carbon Using Neutrinos from Stopped Muon Decay

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Measurement of Neutrino Electron Scattering and Inverse Beta-Decay of Carbon Using Neutrinos from Stopped Muon Decay LA—-1226 2-T DE92 011451 Measurement of Neutrino Electron Scattering and Inverse Beta-Decay of Carbon Using Neutrinos from Stopped Muon Decay Daniel A. Krakauer* 'Collaborator at Los Alamos. Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439. Acknowledgements I'd like to begin with a general acknowledgement to the E225 collabora- tion. I thoroughly enjoyed working with this group, which was not too large, very friendly and composed of people with good taste in physics. Many, if not all, of you will find results of work inspired, suggested, or actually ac- complished by you. Thank you. I am grateful for the leadership and physical intuition brought to this experiment by the late Herb Chen. Prof. Chen was the driving force be- hind this research, even throughout his long illness. I am sad that he is no longer with us and know that this work in particular has suffered without his attention. I thank my colleagues at UC-Irvine for doing the bulk of processing, cal- ibration and analysis of the neutrino scattering data. Besides able general supervision of the analysis effort, Dr. Richard Allen provided an incredible wealth of subroutine libraries and programs that enabled this research. His contributions to all aspects of this experiment, from design of the FCMs to installing the ONLINE data acquistion to wrapping up the final physics results, can not be overestimated. Dr. Wen-Paio Lee provided tireless in- vestigations to rid the data and Monte Carlo of systematic inconsistencies. Along the way he incorporated the run-by-run features into the Monte Carlo simulation and provided plenty of food for thought whenever one was hun- gry for controversy. Dr. Xing-Qi Lu saved me many times from my own errors in the data analysis. His work on the final energy calibrations and the neutrino-carbon signal were essential to the final results. Dr. Michael Potter, who managed to avoid the pitfalls of grad school and get out on time, was the source of much of the Monte Carlo code, particularly the FCM simulation, as well as the data acquistion hardware/software for the flux calibration experiment. This work contains more figures and numbers than I care to admit that were originally found in his thesis. Leaving the UCI group for the last time, I bid fond farewell to Dr. Peter Doe and Dr. Keh Chung Wang, whos' hardware magic worked from day 1. And having written chapter 3 of this text, I take back any disparaging comments to PJD about the NIM paper, which suddenly seems remarkably concise and complete. Moving on to Los Alamos, I must admit that contrary general graduate student rules, I really liked it out there. Not the least of the pleasures was the supportive and interesting enviroment provided by my LANL collabo- rators. I particularly thank Dr. Robert Burman, both for such mundane items as writing the complex Monte Carlo to determine the actual neutrino flux, and more sublime efforts like making sure I had an office. Although Dr. James Frank unfortunately left for Brookhaven shortly after I arrived, I thank him for introducing Sara and me to the local JCC. That the experiment worked was due in large part to the efforts of Nance (Colbert) Briscoe, Neil Thompson and Scott DeLay. Not only did they put the thing together, and put it back together after I messed with it, they VI made it fun to go in for shifts. I already miss daily coffee and Empire with Neil, et al. Thanks to Jim Sena who spent many hours keeping the MWPCs working and many more providing tech support for the calibration experi- ment. Before coming home to Maryland, I want to thank Dr. T. W. Donnelly of MIT for very kindly provided his programs and detailed inputs for com- puting neutrino-nuclear reaction cross-sections. His careful explanations and discussions were very helpful, and the programs were vital to complet- ing this work. I apologize if I have misrepresented or misinterpreted those results. I thank Dr. Joey Donahue of LANL for his efforts on behalf of the neutrino calibration experiment. Dr. Elton Smith also contributed greatly to the calibration experiment and to the subsequent beam-stop Monte Carlo simulation. Outside of the collaboration, I'd like to thank the members of the Cygnus collaboration, particularly Brenda Dingus and Jordan Goodman. That ex- periment providing me something to complain about while worring about the hardware in Los Alamos, and something interesting to think about when I got bored with this work back in Maryland. I won't mention the fact that you have doubled my publication list. And thanks for getting my name in the Times, too. The University of Maryland High Energy Physics Group provided gen- erous support and encouragement throughout this work, for which I thank Prof. George Snow in p irticular. Thanks also for the kind abuse and ulti- Vll mate deadline which helped finalize these results. I would like to mention that the staff at all three institutions Irvine, Los Alamos, and especially Maryland worked wonders at keeping me out of trouble. Now almost home, it is finally time to thank my advisor, Dr. Richard Talaga. I thank him especially for allowing me the freedom to explore my ideas and take charge (if that's what you call it) of my efforts. Yet, when I needed it he could cut to the quick, put me back on the right track or keep me moving towards the (real) goals. I look forward to working with him again at Argonne or elsewhere down the road. vm Table of Contents 1 Introduction 1 A Physics Objectives 2 B Summary of the Experiment 12 2 Theoretical Aspects Of Neutrino Scattering 17 A The Weinberg-Salam-Glashow Model 17 B Neutrino-Electron Elastic Scattering 19 C Neutrino-Induced Nuclear Transitions 26 3 Experimental Design 29 A The Neutrino Beam 31 B Overview of Neutrino Detector 36 C Scintillation Counters 40 D Flash Chamber Modules 47 E Massive Shielding 57 F MWPC Anti-coincidence System 61 F.I Single Counter Construction 62 F.2 Installation 66 F.3 Veto Logic 69 F.4 Data Storage / CAMAC Read-out 74 F.5 Gas Tests 75 IX 4 Experimental Aspects of Neutrino Scattering : Signals and Backgrounds 81 A Neutrino Signals 81 A.I ve~ Reactions 85 A.2 Comments on Inverse-/? Reactions 89 12 A.3 ue C Reactions 90 13 A.4 veA {A= C, "Al, Cl} Reactions 94 A.5 Reactions with Iff, 2D 99 B Backgrounds 100 B.I Beam-Associated Backgrounds 102 B.2 Cosmic-Ray Backgrounds 105 5 Data Collection, Calibration, and Reduction 109 A Trigger Conditions 109 A.I Neutrino Triggers 110 A.2 Stopped-Muon Decay Triggers 115 A.3 Through-Going Muon Triggers 117 A.4 Other Calibration Triggers 118 B Data Acquisition / Run Statistics 123 C Calibration and Offline Analysis 127 C.I Track Fitting , 128 C.2 Energy Calibration 129 D Data Reduction Techniques 140 D.I Cuts Against Obvious Backgrounds 141 D.2 Electron Identification- dE/dX 153 D.3 Final Electron Cuts 153 List of Tables 1 Distribution of Neutrino Targets in the Detector 37 2 Information Recorded by Detector Components 38 3 Online Threshold Levels 44 4 MWPC Counters per Wall 67 5 Veto Rate and Inefficiency vs. Majority Logic Level 72 6 Reaction Rates for Different Targets 83 7 12N(gs) Decay Scheme 93 8 Non-Neutrino Induced Background Rates 101 9 Trigger Requirements 110 10 Event Rates Before and After Shielding Improvements . 120 11 Data Collection Statistics (Events and Livetimes) 125 12 Beam Exposure During Each Run Period 126 13 Chi-Squared for Fits to Gain Drifts 137 14 Data Reduction 142 15 Events Removed by Specific Cuts 143 12 12 16 Additional Cuts Used To Obtain uc C -> e~ N(gs) Event Sample 158 12 17 Data Reduction to vc C Event Sample 162 12 12 18 ve C -> e~ N{gs) Signal vs. Threshold 179 XI 12 12 6 The t/e C -> e~ N(ga) Signal 157 A Analysis Procedure 158 B Investigation of Potential Backgrounds 172 C Investigations into Systematic Uncertainties of the Analysis . 181 D Measured Cross-section 186 7 The ue~ -> ve~ Signal 188 A Fit to Observed Distributions 189 B Tests for Systematic Bias 197 C Subtraction of vMe~ —• fMe~ and FMe~ —> V^e~ Event Rate . 202 8 Physics Results from vee~ —> uee~ Observations 206 A Remarks on Experimental Acceptance 207 B Total Cross-section, cr(vce~ —• vee~ ) 208 C The NC/CC Interference 214 D The Weak Neutral Current Parameters sin2 0w and (gv,9A) 217 E Limits on the Neutrino Magnetic Moment 218 F Summary 222 Appendix I Monte Carlo Simulation 224 A Overview 224 B Physical Reactions Modeled 226 C Detector Parameters and Translation Routines 235 D Checking the Simulation 238 References 241 XII 12 12 19 Systematic Uncertainties For the ve C ~* e~ N(gs) Anal- ysis 185 20 Number of Muon-(anti)neutrino Electron Events 203 21 Parametrization of Neutrino-Electron Cross-sections 209 22 Systematic Uncertainties for the i/ee~ —> i/ee~ Analysis . 213 23 Nuclear Reactions Simulated by the Monte Carlo 232 24 Calibration Events Used for Simulation Routines 237 xiu List of Figures 1 Feynman Diagram for ute —> uee~ 2 2 Feynman Diagrams for Processes Involving the NC/CC In- terference 4 12 12 3 The i/e + C -* e~ + N Reaction 8 4 Schematic View of the Neutrino Detector 13 5 Processes that Measure ||ACC|]2 and \\ANC\\2 23 6 The LAMPF Beam-stop Neutrino Area 30 7 Cutaway View of Detector and Shielding 32 8 Neutrino Energy Spectra 35 9 Energy Resolution as a Function of Electron Energy ....
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