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

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86 4. Measurement of ✓ 13 with the Double Chooz far detector tel-00821629, version 1 - 11 May 2013 target as the fiducial volume for ¯⌫ e searches through neutron capture on Gd. In order to reduce the contamination from muon correlated background and cosmogenic isotopes, further conditions are applied. A multiplicity condition to reject correlated events before (after) the prompt (delayed) is defined as no additional trigger from 100 µs preceding the prompt candidate to 400 µs after it [34]. The IBD-like events in coincidence with an OV hit are tagged as correlated background and rejected, such condition is referred as OV veto. The correlated background analysis described in Sec. 4.3.3, estimates a background reduction of about 28 %. The OV veto increase the dead time exposure by < 0.6 % [45]. The IBD-like events within 0.5 s from an high energy muon, defined as an energy deposition bigger than 600 MeV, are tagged as cosmogenic radioisotopes and rejected. The cosmogenic background analysis described in Sec. 4.3.2, estimates a background reduction of about 40 %. The long veto upon high energy muons introduce a dead time of 4.89 ± 1.7 %, estimated by evaluating the fraction of ¯⌫ e candidates, over the total, found in a random 0.5 s time window [98]. The energy correlation between the prompt and the delayed events is shown in Fig. 4.8. The y-axis shows the Gd-peak between [7, 9] MeV and its Compton edge extending to low energies. The x-axis shows the prompt spectrum between [0.7, 15] MeV with a maximum at about 3 MeV, as expected for reactor-¯⌫ e . About 8249 ¯⌫ e candidate are found for 227.93 days of detector live time, giving an averaged rate of 36.2 ± 0.4 candidates/d [77]. The ¯⌫ e rate as a function of day is shown in Fig. 4.9 (black points) with MC expected rate (blue point). The discrepancies between data and MC are due to the background contamination, which is not subtracted. Time periods where the ¯⌫ e rate is lower of about 50 %, corresponds to about 87 d (⇠ 40 % of detector live time) where one of the two reactor cores was running at low power (< 20 %) or was not running at all. The lower points around day 190 corresponds to the 22nd October 2011, when both reactors were o↵ for approximately 22 h. 4.2.1 Selection cuts summary In summary, the ¯⌫ e searches are performed applying the following selection: No external triggers Light noise cuts: • Q max /Q tot < 0.09 • RMS(T start )< 40 ns Prompt candidate: • E in [0.7, 12.2] MeV
4.2 ¯⌫ e signal selection 87 Neutrino rate ) -1 100 Neutrino Rate (day 80 60 Double Chooz preliminary Expected rate Measured rate 40 20 0 0 50 100 150 200 250 300 Day tel-00821629, version 1 - 11 May 2013 Figure 4.9: Observed (black points) and simulated (blue points) ¯⌫ e rate in function of data taking day. The background is not subtracted from the data. The fluctuation of the ¯⌫ e rate are due to fluctuations of the power delivered by the reactor. About 8249 ¯⌫ e candidate are found for 227.93 days of detector live time, giving an averaged rate of 36.2 ± 0.4 candidates/d [77]. Delayed candidate: • Delayed E in [6; 12] MeV • Delayed Q max /Q tot < 0.05 Time correlation: • t in [2; 100] µs Multiplicity cuts: • No valid triggers in the 100 µs preceding the prompt candidate • The time window from 2 µs to 100 µs following the prompt can contain only the delayed candidate. • No valid triggers in [100, 400] µs after the prompt candidate Reduce muon-correlated events: • t(µ) > 1000 µs after a muon (E ID > 30 MeV or Q ID > 10 4 DUQ ) • No coincidence with Outer Veto hit Reduce cosmogenic radioisotopes: • t(µ) > 0.5 s after showering muon (E >600 MeV)
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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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Page 35 and 36: 2.5 The problem with the neutrino m
Page 37 and 38: 2.6 Summary and open questions 37 s
Page 39 and 40: In the next future, reactor experim
Page 41 and 42: Chapter 3 The Double Chooz experime
Page 43 and 44: 3.1 The Double Chooz detector 43 to
Page 45 and 46: 3.1 The Double Chooz detector 45 te
Page 47 and 48: 3.1 The Double Chooz detector 47 it
Page 49 and 50: 3.1 The Double Chooz detector 49 te
Page 51 and 52: 3.2 The detector read-out 51 40 m o
Page 53 and 54: 3.3 The online system 53 IV trigger
Page 55 and 56: 3.3 The online system 55 tions as s
Page 57 and 58: 3.3 The online system 57 tel-008216
Page 59 and 60: 3.4 The calibration system 59 tel-0
Page 61 and 62: loosing their kinetic energy 3 and
Page 63 and 64: 3.5 Reactor neutrino flux simulatio
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: 4.2 ¯⌫ e signal selection 85 Pro
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
Page 95 and 96: 4$&14+#':"'$"$468'#21%$;' ! $"$468'
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
Page 103 and 104: 4.6 Final fit and measurement of
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 and 118: 5.4 Fast Neutrons analysis 117 bigg
Page 119 and 120: 5.4 Fast Neutrons analysis 119 5.4.
Page 121 and 122: 5.4 Fast Neutrons analysis 121 tel-
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
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5.4 Fast Neutrons analysis 137 tel-
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5.5 Stopping Muon analysis 139 5.5.
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5.5 Stopping Muon analysis 141 tel-
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5.5 Stopping Muon analysis 143 tel-
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5.5 Stopping Muon analysis 145 Sour
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5.5 Stopping Muon analysis 147 belo
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5.5 Stopping Muon analysis 149 The
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5.6 Estimation of correlated backgr
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5.7 Conclusion 157 5.7 Conclusion t
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Chapter 6 Conclusions tel-00821629,
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161 • The SM analysis could be im
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Chapter 7 Contributions to Double C
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165 from this study and from [64] f
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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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