A Search for Long-Lived Charged Particles in Cosmic Rays

169 Pages·2012·8.23 MB·English

A Search for Long-Lived Charged Particles
in Cosmic Rays
BY
MARIO CAMUYRANO
M.S. (University of Illinois at Chicago, United States) 2008
THESIS
Submitted in partial fulfillment of the requirements
for the degree of Doctor of Philosophy in Physics
in the Graduate College of the
University of Illinois at Chicago, 2012
Chicago, Illinois
Defense Committee:
Mark Adams, Chair and Advisor
Nikos Varelas
David Hofman
Cecilia Gerber
Diego Casa, Argonne National Laboratory
Copyright by
Mario Camuyrano
2012
To Laura Virginia ... and
to the ones that left too early, with too many things to do yet.
And the ones that take too long to do anything.
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ACKNOWLEDGMENT
I want to thank Laura Virginia and all our big family, my mother Rosario, mother in
law Maria Laura, father Mario, father in law Dardo, grandmother Cristina and grandfather
Salvador, sister Maria Victoria, brother and sister in law Rodolfo and Mariana, nieces Victoria
and Virginia, nephew and nieces Julian, Malena and Felicitas. Uncle and aunts, Bambina,
Marcela, Pascual, Alicia and cousins Gabriela, Martin, Santiago, Agustin, Diego and Claudia...
for all their unconditional love and support.
I want to thank Mark for all this time and dedication and to transmitting me his passion for
astronomy (this is not an astronomy thesis though). Also I am grateful with all the UIC HEP
people for listening with interest to all my talks. All the committee members for their time.
Cecilia for all her advises and interest, Nikos for his interest in the subject and all his questions
and ideas. Dave for all his help, advise and great support, and Diego for his generosity always.
I want to thank Victor to introduce me to the CLs world. And Wade Fisher for his time.
I want to thank very specially all my good friends here and in Argentina. Specially Gustavo
and Julia who invited me to UIC and facilitated me everything, including housing. The friends
that are always there: Diego, Natalia, Jaesung, Tim, Ahmet, Francisco, Sankar, Nico, Carlos,
Jeronimo, Daniel, Alejandro, Mastro, Pablo, Richard, Ricardo, Nestor, Gabriel, Ariel, German,
Cosme, Emilio, Cora, Alejo, Miro, Edu, Tefi, Moni, Miri, Robert, James, Gustavo, Ruben.
Melodie, Luis, Derrick and the friends I forget to mention.
I want to thank all that take the time to read this thesis.
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TABLE OF CONTENTS
CHAPTER PAGE
1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.3 Cosmic rays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Muon lifetime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.4.1 Muon lifetime in matter . . . . . . . . . . . . . . . . . . . . . . . 5
1.5 Long-lived particles searches . . . . . . . . . . . . . . . . . . . . 11
1.6 Thesis outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2 EXPERIMENTAL PROCEDURE . . . . . . . . . . . . . . . . . . . . . 15
2.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2 Experiments setup . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3 DATA ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.1 General procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.1.1 Trigger definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.1.2 Processing the raw data . . . . . . . . . . . . . . . . . . . . . . . 34
3.2 Hardware studies . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.3 Detector studies . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4 RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.1 Muon lifetime measurement . . . . . . . . . . . . . . . . . . . . 48
4.1.1 Muon capture rate . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.1.2 Muon lifetime East-West asymmetry . . . . . . . . . . . . . . . 52
4.2 Setting limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.2.1 Cleaning the data sample . . . . . . . . . . . . . . . . . . . . . . 59
4.2.2 Lifetime spectrum comparison . . . . . . . . . . . . . . . . . . . 63
4.2.2.1 Muon decays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.2.2.2 Muon decays within large EAS . . . . . . . . . . . . . . . . . . . 68
4.2.3 Negative log-likelihood implementation . . . . . . . . . . . . . . 75
4.3 Results for SB and S1’ samples . . . . . . . . . . . . . . . . . . 84
4.3.1 Systematic errors estimation . . . . . . . . . . . . . . . . . . . . 95
4.4 Results with extensive air shower S tag and J tag . . . . . . . 98
5 EXTENDED DECAY TIME SEARCH . . . . . . . . . . . . . . . . . 100
5.1 Background estimation . . . . . . . . . . . . . . . . . . . . . . . 102
5.2 Signal plus background estimation . . . . . . . . . . . . . . . . 110
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TABLE OF CONTENTS (Continued)
CHAPTER PAGE
5.2.1 Systematic errors estimation . . . . . . . . . . . . . . . . . . . . 111
5.3 Confidence limits determination applied to very long lifetimes 111
6 CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
APPENDICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Appendix B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
Appendix C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
CITED LITERATURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
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LIST OF TABLES
TABLE PAGE
I MUON ENERGY LOSS IN AIR . . . . . . . . . . . . . . . . . . . . . 9
II EXPERIMENT RATE COMPARISON . . . . . . . . . . . . . . . 23
III AVERAGE LIFETIME EAST-WEST ASYMMETRY . . . . . . . . 58
IV MUON DECAYS AND BACKGROUND COMPARISON . . . . . . 67
V NUMBER OF MUON DECAYS COMPARISON . . . . . . . . . . . 74
VI BACKGROUND 2σ-FLUCTUATION IN MUON LIFETIME . . . . 97
VII EXPERIMENT EVOLUTION RATE COMPARISON . . . . . 123
VIII FIT SELF CONSISTENCY TEST . . . . . . . . . . . . . . . . . . . . 147
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LIST OF FIGURES
FIGURE PAGE
1 Elementary particles in the Standard Model . . . . . . . . . . . . . . . . 3
2 Content of the universe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3 Primary cosmic radiation composition . . . . . . . . . . . . . . . . . . . . 6
4 Estimated vertical fluxes of particles in cosmic ray air showers . . . . . 7
5 Spectra of atmospheric muon on the ground . . . . . . . . . . . . . . . . 8
6 Electron capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7 Experimental muon charge ratio . . . . . . . . . . . . . . . . . . . . . . . . 10
8 Montecarlo simulation of a long-lived charged particle decay. . . . . . . 17
9 W-T array setup sketch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
10 Experimental layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
11 Synchronization of CRs through DAQs with different GPSs . . . . . . . 28
12 Time distribution of W-T across DAQs . . . . . . . . . . . . . . . . . . . 29
13 Signal, raw data and reconstructed data . . . . . . . . . . . . . . . . . . . 30
14 Detector calibration plateaus . . . . . . . . . . . . . . . . . . . . . . . . . . 32
15 Time distributions for W-T counters . . . . . . . . . . . . . . . . . . . . . 33
16 Data flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
17 S1’ 16 channel output and event display . . . . . . . . . . . . . . . . . . . 37
18 Montecarlo simulation for randoms in a simulated long-lived charged
particle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
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LIST OF FIGURES (Continued)
FIGURE PAGE
19 Event time calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
20 DAQ 5000 frequency correction . . . . . . . . . . . . . . . . . . . . . . . . 42
21 DAQ 6000 PPS delay respect to the GPS latched time . . . . . . . . . . 43
22 Muon lifetime turn on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
23 Trigger bias ”hump” in the muon lifetime . . . . . . . . . . . . . . . . . . 47
24 Muon capture rate fit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
25 Muon East-West asymmetry . . . . . . . . . . . . . . . . . . . . . . . . . . 54
26 Muon East-West flux estimation . . . . . . . . . . . . . . . . . . . . . . . . 56
27 S1’ and SB 1-hour rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
28 S1’ and SB rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
29 Sources of fluctuation of muon rates at sea level . . . . . . . . . . . . . . 62
30 Montecarlo simulation of a long-lived charged particle. . . . . . . . . . . 63
31 Lifetime spectrum comparison . . . . . . . . . . . . . . . . . . . . . . . . . 65
32 Lifetime spectrum comparison . . . . . . . . . . . . . . . . . . . . . . . . . 66
33 Lifetime EAS S-tag, no veto . . . . . . . . . . . . . . . . . . . . . . . . . . 69
34 Lifetime EAS S-tag, no veto . . . . . . . . . . . . . . . . . . . . . . . . . . 70
35 Lifetime EAS S-tag, with veto . . . . . . . . . . . . . . . . . . . . . . . . . 71
36 S1’ and SB lifetime fits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
37 NLLR 95% Confidence Limits . . . . . . . . . . . . . . . . . . . . . . . . . 80
38 NLLR 95% Confidence Limits example . . . . . . . . . . . . . . . . . . . . 81
39 NLLR signal selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
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LIST OF FIGURES (Continued)
FIGURE PAGE
40 Lifetime background simulation . . . . . . . . . . . . . . . . . . . . . . . . 86
41 CHAMP simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
42 95% Confidence Limits for SB sample . . . . . . . . . . . . . . . . . . . . 89
43 95% Confidence Limits for S1’ and SB sample . . . . . . . . . . . . . . . 91
44 95% Confidence Limits for SB and S1’ sample . . . . . . . . . . . . . . . 92
45 95% Confidence Limits for S1’ and SB sample . . . . . . . . . . . . . . . 94
46 W clock frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
47 95% Confidence Limits for large EAS . . . . . . . . . . . . . . . . . . . . . 99
48 Extended-time possible trajectories . . . . . . . . . . . . . . . . . . . . . . 101
49 Background estimation of simulation . . . . . . . . . . . . . . . . . . . . . 106
50 Data, simulation and estimation for background . . . . . . . . . . . . . . 107
51 Data with estimation for background subtracted . . . . . . . . . . . . . . 108
52 Estimation of background for short lifetimes . . . . . . . . . . . . . . . . 109
53 Long lifetime limits for SB . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
54 Long lifetime limits for S1’ . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
55 Experimental evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
56 Decay simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
57 Lifetime versus number of bins . . . . . . . . . . . . . . . . . . . . . . . . 128
58 Lifetime uncertainty versus number of bins . . . . . . . . . . . . . . . . . 130
59 Modified Stabilized LS fit versus number o bins . . . . . . . . . . . . . . 131
60 Modify fit uncertainty vs. number of pseudo-experiments . . . . . . . . . 134
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