Etude et impact du bruit de fond corrÃ©lÃ© pour la mesure de l'angle ...

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118 5. Correlated background ID trigger both ID and IV are read-out, thus the IV detection threshold is lowered below its self-trigger threshold (⇠ 10 MeV). The IV is then sensible to FNs which deposit energy through proton recoil or by H capture. The FN analysis is performed on the ¯⌫ e candidate selected by requiring the prompt energy in [0.7, 30] MeV and applying the FN/SM separation cut t>10 µs. The OVV is omitted in order to increase the statistics of the IVT sample and to allow the comparison with the results obtained with the OVT. The OVV will be applied later. tel-00821629, version 1 - 11 May 2013 Figure 5.6: Fast neutron event topology as generated by muons creating neutron with high multiplicity. The FN interacting in the ID mimic the ¯⌫ e signature. The IV is sensitive to FN via proton recoil or neutron capture on H, which allow the FN to be tagged.
5.4 Fast Neutrons analysis 119 5.4.1 IV Tagging Since the IV is a scintillator detector, nearly all energy deposited by a FN, or any other particle, is visible without any detection threshold. The tagging condition between the ID and the IV implicitly define a time coincidence within the read-out time window of 256 ns. The IV PMT dark noise, with a rate of ⇠ 10 kHz, is expected to produce accidental tagging with a negligible rate of ⇠ 2 ⇥ 10 4 Hz by requiring a time coincidences in such short time window. However, coincidences between ID energy deposition and natural radioactivity in the IV contaminates the low energy part of the IV spectrum, . 1 MeV, as shown in Fig. 5.7. A tagging threshold > 1 MeV would select a rather clean sample of FN but would reduce the sample statistics, while a threshold < 1 MeV would not easily allow to distinguish physics events from natural radioactivity gamma. tel-00821629, version 1 - 11 May 2013 Figure 5.7: The IV energy spectrum in coincidence with a prompt energy deposition in the ID. The lower part of the spectrum, . 1 MeV, is dominated by natural radioactivity gamma and PMT dark noise. An alternative tagging condition based on the number of IV PMT hits has been proposed in [43] and used in this analysis. The multiplicity condition implicitly define a charge threshold, independent from the absolute energy scale of the IV. A rather large energy deposition within the field of view of at least 2 IV PMTs, in coincidence with a prompt-like event in the ID, is more likely caused by correlated physics. Therefore, tagging events with 2 or more PMT hits allow to reduce accidental coincidences with natural radioactivity, since low energy events are expected to hit only one PMT. Fig. 5.8 shows the IV energy spectrum obtained for di↵erent values of hit multiplicity. Requiring the PMT multiplicity to be bigger than 2 rejects
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UNIVERSITÉ DENANTES FACULTÉ DES S
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tel-00821629, version 1 - 11 May 20
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Abstract tel-00821629, version 1 -
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Acknowledgments Since so many peopl
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Contents 1 Introduction 13 tel-0082
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CONTENTS 11 tel-00821629, version 1
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Chapter 1 Introduction tel-00821629
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15 tel-00821629, version 1 - 11 May
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Chapter 2 Neutrino physics tel-0082
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2.2 Neutrino history in brief 19 ma
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2.3 Neutrino oscillation, the theor
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2.4 Measuring neutrino oscillation
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3-flavour oscillations The dominant
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After the Sun, the other main natur
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2.5 The problem with the neutrino m
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2.6 Summary and open questions 37 s
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In the next future, reactor experim
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Chapter 3 The Double Chooz experime
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3.1 The Double Chooz detector 43 to
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3.1 The Double Chooz detector 45 te
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3.1 The Double Chooz detector 47 it
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3.1 The Double Chooz detector 49 te
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3.2 The detector read-out 51 40 m o
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3.3 The online system 53 IV trigger
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3.3 The online system 55 tions as s
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3.3 The online system 57 tel-008216
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3.4 The calibration system 59 tel-0
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loosing their kinetic energy 3 and
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3.5 Reactor neutrino flux simulatio
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3.5 Reactor neutrino flux simulatio
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Page 69 and 70: 3.8 Data reconstruction 69 A dedica
Page 71 and 72: Regarding the pulse information, th
Page 73 and 74: 3.8 Data reconstruction 73 tel-0082
Page 75 and 76: 3.8 Data reconstruction 75 Gain (ch
Page 77 and 78: 3.9 Conclusions 77 tel-00821629, ve
Page 79 and 80: Chapter 4 Measurement of ✓ 13 wit
Page 81 and 82: 4.1 Data sample 81 create a signal
Page 83 and 84: 4.2 ¯⌫ e signal selection 83 Liv
Page 85 and 86: 4.2 ¯⌫ e signal selection 85 Pro
Page 87 and 88: 4.2 ¯⌫ e signal selection 87 Neu
Page 89 and 90: 4.3 Backgrounds 89 energy spectrum
Page 91 and 92: 4.3 Backgrounds 91 tel-00821629, ve
Page 93 and 94: 4.4 Selection e ciencies and system
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Page 97 and 98: 4.4 Selection ! e ciencies and syst
Page 99 and 100: 4.5 Data analysis summary 99 4.4.3
Page 101 and 102: 4.6 Final fit and measurement of
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Page 105 and 106: 4.7 Summary and Conclusions 105 tel
Page 107 and 108: Chapter 5 Correlated background tel
Page 109 and 110: 5.1 Measuring correlated background
Page 111 and 112: 5.2 High energy analysis 111 in a l
Page 113 and 114: 5.2 High energy analysis 113 tel-00
Page 115 and 116: 5.3 OV Tag analysis 115 The t cut v
Page 117: 5.4 Fast Neutrons analysis 117 bigg
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Page 123 and 124: 5.4 Fast Neutrons analysis 123 esti
Page 125 and 126: 5.4 Fast Neutrons analysis 125 Corr
Page 129 and 130: 5.4 Fast Neutrons analysis 129 Prom
Page 131 and 132: 5.4 Fast Neutrons analysis 131 lect
Page 133 and 134: 5.4 Fast Neutrons analysis 133 mari
Page 139 and 140: 5.5 Stopping Muon analysis 139 5.5.
Page 141 and 142: 5.5 Stopping Muon analysis 141 tel-
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Page 145 and 146: 5.5 Stopping Muon analysis 145 Sour
Page 147 and 148: 5.5 Stopping Muon analysis 147 belo
Page 149 and 150: 5.5 Stopping Muon analysis 149 The
Page 151 and 152: 5.6 Estimation of correlated backgr
Page 157 and 158: 5.7 Conclusion 157 5.7 Conclusion t
Page 159 and 160: Chapter 6 Conclusions tel-00821629,
Page 161 and 162: 161 • The SM analysis could be im
Page 163 and 164: Chapter 7 Contributions to Double C
Page 165 and 166: 165 from this study and from [64] f
Page 167 and 168: List of Figures tel-00821629, versi
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LIST OF FIGURES 169 tel-00821629, v
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List of Tables 3.1 Mean energy rele
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Bibliography [1] [2] tel-00821629,
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BIBLIOGRAPHY 183 [31] J.K. Ahn et a
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BIBLIOGRAPHY 185 [61] W. Hampel et
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BIBLIOGRAPHY 187 [92] A. Stueken et
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