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

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176 LIST OF FIGURES 5.18 IVT FN prompt spectrum (black histogram) and the stacked expected background contamination from events (green) and ¯⌫ e +IV /n events (violet). Black points shows the FN spectrum upon background subtraction. In order to minimise distortion on the IVT FN spectral shape, the remaining background contamination has been subtracted (black points). The error bars account for statistical uncertainties. . . . . . . 133 tel-00821629, version 1 - 11 May 2013 5.19 IVT FN spectrum fit with flat model (top) and sloped linear model (bottom). The flat linear model gives 2 /ndf =9.4/9 and a fit probability of ⇠ 40 %, while the sloped linear model gives 2 /ndf =7.3/8 and a fit probability of ⇠ 50 %. Since the sloped linear model shows a better agreement with the data, it is assumed as FN spectral shape. A total rate of (0.33 ± 0.16) cpd is found. . . . . . . . . . . . . . . . . . . . . 135 5.20 IVT spectrum and related background for for di↵erent IVT multiplicity condition. Increasing the multiplicity threshold the tagging e ciency decrease, then the number of tagged events and the expected background decrease. The IVT spectra upon background subtraction are fitted with a sloped linear models. The spectral shape does not change by changing the IVT condition. The FN rate change up to 25 %, however, such increase is within uncertainty. . . . . . . . . . . . . . . . 137 5.21 Comparison between SM candidates (black histograms) and HELN sample obtained by performing o↵-time selection (violet points). The low energy part of the prompt spectrum (top left) shows the characteristic shape of natural radioactivity gamma and is well reproduced by the o↵-time sample. O↵-time coincidence with higher energy prompt candidate are also observed. The delayed energy spectrum (top right) shows less HELN contamination in the low energy part of delayed spectrum, < 40 MeV, while the o↵-time selection reproduce well the higher part of the spectrum, suggesting more contamination. The prompt delayed time distribution shows a flat distribution for the o↵-time selection (bottom left) while the on-time sample (bottom right) shows the correlated distribution from SM, with a time constant of 1.9 ± 0.2 µs. . . . 140
LIST OF FIGURES 177 tel-00821629, version 1 - 11 May 2013 5.22 Comparison between the spatial distributions of SM candidates (black histograms) and HELN sample obtained by performing o↵-time selection (violet points). The on-time prompt distributions (top left and right) shows clear excess of events below the detector chimney, as expected by SM, while the o↵-time distribution shows events distributed more widely in the detector, as expected from natural radioactivity gammas. The delayed vertex distribution (bottom left and right) shows an excess below the chimney and some others peaks at fixed positions. Such peaks are well reproduced by the o↵-time selection and are due to LN. The packed distribution is an artefact of the vertex reconstruction algorithm, which reconstruct the LN vertex close to the PMT responsible of the light emission. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 5.23 Q max /Q tot variable as a function of the prompt (left) and delayed (right) energy for SM candidates (black histograms) and HELN sample obtained by performing o↵-time selection (violet points). The SM prompt candidates shown Q max /Q tot distribution typical for physics events, while the delayed events show an excess of event between [0.04, 0.06] with 1/E behaviour.142 5.24 Prompt (left) and delayed (right) SM spectrum upon subtraction of HELN contamination. The error bars account for the statistical uncertainty of the data sample and the systematic uncertainty induced by the spectral subtraction. . . . . . . . 142 5.25 SM spectrum fit with flat model (top) and sloped linear model (bottom). The flat linear model gives a 2 /ndf =7.1/8 and a fit probability of ⇠ 52 % while the sloped linear model gives a 2 /ndf = 6.9/7 and a fit probability of ⇠ 44 %. Both models shown compatible results however the more generic sloped shape is used as spectral shape for SM background, since there is no physical reason for a flat SM spectrum. A total rate of (0.62 ± 0.20) cpd is found. . . . . . . . . . . . . . 144 5.26 Digital Q max /Q tot vs energy for prompt (left column) and delayed (right column) for HELN events (top row) and SM candidates (bottom row). Delayed events are clearly distributed above Digital Q max /Q tot of about 40 while prompt events appear to be below such value. As discussed previously, the Digital Q max /Q tot distributions confirm that the delayed candidates at high energy are the most a↵ected by HELN contamination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
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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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3.8 Data reconstruction 69 A dedica
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Regarding the pulse information, th
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3.8 Data reconstruction 73 tel-0082
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3.8 Data reconstruction 75 Gain (ch
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3.9 Conclusions 77 tel-00821629, ve
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Chapter 4 Measurement of ✓ 13 wit
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4.1 Data sample 81 create a signal
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4.2 ¯⌫ e signal selection 83 Liv
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4.2 ¯⌫ e signal selection 85 Pro
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4.2 ¯⌫ e signal selection 87 Neu
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4.3 Backgrounds 89 energy spectrum
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4.3 Backgrounds 91 tel-00821629, ve
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4.4 Selection e ciencies and system
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4$&14+#':"'$"$468'#21%$;' ! $"$468'
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4.4 Selection ! e ciencies and syst
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4.5 Data analysis summary 99 4.4.3
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4.6 Final fit and measurement of
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4.6 Final fit and measurement of
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4.7 Summary and Conclusions 105 tel
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Chapter 5 Correlated background tel
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5.1 Measuring correlated background
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5.2 High energy analysis 111 in a l
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5.2 High energy analysis 113 tel-00
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5.3 OV Tag analysis 115 The t cut v
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5.4 Fast Neutrons analysis 117 bigg
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5.4 Fast Neutrons analysis 119 5.4.
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5.4 Fast Neutrons analysis 121 tel-
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5.4 Fast Neutrons analysis 123 esti
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Page 165 and 166: 165 from this study and from [64] f
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Page 181 and 182: Bibliography [1] [2] tel-00821629,
Page 183 and 184: BIBLIOGRAPHY 183 [31] J.K. Ahn et a
Page 185 and 186: BIBLIOGRAPHY 185 [61] W. Hampel et
Page 187: BIBLIOGRAPHY 187 [92] A. Stueken et
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