1 | \documentclass{JINST} |
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2 | %\usepackage{graphicx} |
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3 | \usepackage[pdftex]{graphicx} |
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4 | \usepackage[figuresright]{rotating} |
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5 | \usepackage[T1]{fontenc} |
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6 | \usepackage{eurosym} |
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9 | %used explicitly in the text |
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10 | \newcommand{\refTab}[1]{Tab.~\ref{#1}} |
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11 | \newcommand{\refFig}[1]{Fig.~\ref{#1}} |
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12 | \newcommand{\refSec}[1]{Sec.~\ref{#1}} |
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16 | |
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17 | \title{Large underground, liquid based detectors for astro-particle physics in Europe: scientific case and prospects} |
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18 | % |
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19 | |
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20 | \author{First Author$^a$, Second Author$^b$\thanks{Corresponding |
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21 | author.}~ and Third Author$^b$\\ |
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22 | \llap{$^a$}Name of Institute,\\ |
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23 | Address, Country\\ |
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24 | \llap{$^b$}Name of Institute,\\ |
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25 | Address, Country\\ |
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26 | E-mail: \email{CorrespondingAuthor@email.com}} |
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27 | |
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28 | |
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29 | |
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30 | |
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31 | \abstract{ |
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32 | |
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33 | This document reports on a series of experimental and theoretical studies conducted to |
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34 | assess the astro-particle physics potential of three future large-scale particle detectors |
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35 | proposed in Europe as next generation underground observatories. |
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36 | |
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37 | }%end of abstract |
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38 | |
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39 | %\pacs{13.30.a,14.20.Dh,14.60.Pq,26.65.t+,29.40.Gx,29.40.Ka,29.40.Mc,95.55.Vj,95.85.Ry, |
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40 | %97.60.Bw} |
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41 | |
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42 | %\submitto{Journal of Cosmology and Astroparticle Physics} |
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43 | |
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44 | \keywords{Keyword1; Keyword2; Keyword3} |
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45 | |
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46 | \begin{document} |
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47 | %use BST file provided by SPIRES for JHEP and modify it to forbid "to lower case" title |
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48 | \bibliographystyle{Campagne} |
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49 | |
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50 | \section{Physics motivation} |
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51 | \label{sec:Phys-Intro} |
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52 | |
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53 | Our last citation \cite{Genolini:2008uc}..... |
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54 | |
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55 | The RMS error is $\sigma$... |
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56 | |
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57 | |
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58 | Several outstanding physics goals could be achieved by the next generation of large underground observatories |
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59 | in the domain of astro-particle and particle physics, neutrino astronomy and cosmology. |
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60 | Proton decay \cite{Pati:1973rp}, in particular, is one of the most exciting prediction of Grand Unified Theories |
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61 | (for a review see \cite{Nath:2006ut}) aiming at the |
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62 | unification of fundamental forces in Nature. It remains today one of the most relevant open questions |
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63 | of particle physics. Its discovery would certainly represent a fundamental milestone, contributing to clarifying our |
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64 | understanding of the past and future evolution of the Universe. |
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65 | |
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66 | |
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67 | \begin{figure}[htb] |
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68 | \begin{center} |
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69 | \includegraphics[scale=0.5]{./test_figs/varvscycle.pdf} |
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70 | \end{center} |
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71 | \caption{Example of figure PDF} |
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72 | \label{fig:1} |
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73 | \end{figure} |
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74 | |
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75 | |
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76 | |
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77 | |
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78 | \begin{figure}[htb] |
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79 | \begin{center} |
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80 | \includegraphics[scale=0.5]{./test_figs/pulse_snapshot.jpg} |
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81 | \end{center} |
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82 | \caption{Example figure JPEG} |
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83 | \label{fig:2} |
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84 | \end{figure} |
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85 | |
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86 | Several experiments have been built and conducted to search for proton decay but they only yielded lower limits to the proton lifetime. |
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87 | The window between the predicted proton lifetime (in the simplest models typically below $10^{37} $ years) and that excluded |
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88 | by experiments \cite{Kobayashi:2005pe} |
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89 | ($O$($10^{33}$) years, depending on the channel) is within reach, |
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90 | and the demand to fill the gap grows with the progress in other domains of particle physics, astro-particle physics and cosmology. |
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91 | To some extent, also a negative result from next generation high-sensitivity experiments |
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92 | would be relevant to rule-out some of the |
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93 | theoretical models based on SU(5) and SO(10) gauge symmetry or to further constrain the range of allowed parameters. |
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94 | Identifying unambiguously proton decay and measuring its lifetime would set a firm scale for any Unified Theory, narrowing |
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95 | the phase space for possible models and their parameters. This will be a mandatory step to go forward |
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96 | beyond the Standard Model of elementary particles and interactions. |
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97 | |
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98 | Another important physics subject is the physics of |
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99 | %natural (A. Mirizzi 15may07) |
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100 | astrophysical |
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101 | neutrinos, as those from supernovae, from the Sun and from the interaction of primary cosmic-rays with the Earth's atmosphere. Neutrinos are above all important messengers from stars. |
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102 | Neutrino astronomy has a glorious although recent history, from the detection of solar neutrinos |
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103 | \cite{Davis:1968cp,Hirata:1989zj,Anselmann:1992um,Abdurashitov:1994bc,Smy:2002rz,Aharmim:2005gt,Altmann:2005ix} |
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104 | to the observation of neutrinos from supernova explosion, \cite{Hirata:1987hu,Bionta:1987qt,Alekseev:1988gp}, |
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105 | acknowledged by the Nobel Prizes awarded to M. Koshiba and R. Davis. |
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106 | These observations have given valuable information for a better understanding of the functioning |
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107 | of stars and of the properties of neutrinos. However, much more information could be obtained if the energy spectra of |
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108 | stellar neutrinos were known with higher accuracy. |
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109 | Specific neutrino observations could give detailed information on the conditions of the production zone, |
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110 | whether in the Sun or in a supernova. |
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111 | A supernova explosion in our galaxy would be extremely important as the evolution mechanism of the collapsed star |
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112 | is still a puzzle for astrophysics. |
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113 | An even more fascinating challenge would be observing neutrinos from extragalactic supernovae, either from identified sources |
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114 | or from a diffuse flux due to unidentified past supernova explosions. |
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115 | |
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116 | Observing neutrinos produced in the atmosphere as cosmic-ray secondaries |
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117 | \cite{Aglietta:1988be,Hirata:1988uy,Hirata:1992ku,Becker-Szendy:1992hq,Daum:1994bf,Allison:1999ms,Ashie:2005ik} |
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118 | gave the first compelling evidence |
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119 | for neutrino oscillation \cite{Fukuda:1998mi,Kajita:2006cy}, a process that unambiguously points to the existence of new physics. |
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120 | While today the puzzle of missing atmospheric neutrinos can be considered solved, |
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121 | there remain challenges related to the sub-dominant oscillation phenomena. In particular, precise measurements of |
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122 | atmospheric neutrinos with high statistics and small systematic errors \cite{TabarellideFatis:2002ni} |
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123 | would help in resolving ambiguities and degeneracies that hamper the interpretation |
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124 | of other experiments, as those planned for future long baseline neutrino oscillation measurements. |
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125 | |
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126 | Another example of outstanding open questions is that of the knowledge of the interior of the Earth. |
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127 | It may look hard to believe, but we know much better what happens inside the Sun than inside our own planet. |
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128 | There are very few messengers that can provide information, while a mere theory is not sufficient for building a credible model for the Earth. However, there is a new unexploited window to the Earth's interior, |
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129 | by observing neutrinos produced in the radioactive decays of heavy elements in the matter. Until now, only the KamLAND |
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130 | experiment \cite{Araki:2005qa} has been able to study these so-called geo-neutrinos opening the way to a completely new |
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131 | field of research. The small event rate, however, does not allow to draw significant conclusions. |
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132 | |
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133 | The fascinating physics phenomena outlined above, in addition to other important subjects that we will address in the following, |
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134 | could be investigated by a new generation of multipurpose |
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135 | experiments based on improved detection techniques. |
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136 | The envisioned detectors must necessarily be very massive (and consequently large) |
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137 | due to the smallness of the cross-sections and to the low rate of signal events, |
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138 | and able to provide very low experimental background. |
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139 | The required signal to noise ratio can only be achieved in underground laboratories suitably shielded against cosmic-rays |
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140 | and environmental radioactivity. |
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141 | We can identify three different and, to large extent, complementary technologies capable to meet the challenge, based |
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142 | on large scale use of liquids for building large-size, volume-instrumented detectors |
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143 | |
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144 | \begin{itemize} |
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145 | \item Water Cherenkov. |
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146 | As the cheapest available (active) target material, water is the only liquid that is realistic for extremely large detectors, |
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147 | up to several hundreds or thousands of ktons; detectors have sufficiently good resolution in energy, |
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148 | position and angle. The technology is well proven, as previously used for the IMB, Kamiokande and Super-Kamiokande |
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149 | experiments. |
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150 | |
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151 | \item Liquid scintillator. |
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152 | Experiments using a liquid scintillator as active target |
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153 | provide high-energy resolution and offer low-energy threshold. They are |
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154 | particularly attractive for low energy particle detection, as for example solar |
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155 | neutrinos and geo-neutrinos. Also liquid scintillator detectors feature a well established technology, |
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156 | already successfully applied at relatively large scale to the Borexino |
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157 | \cite{Back:2004zn} and KamLAND \cite{Araki:2004mb} experiments. |
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158 | |
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159 | |
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160 | \item Liquid Argon Time Projection Chambers (LAr TPC). |
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161 | This detection technology has among the three the best performance in identifying the topology of |
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162 | interactions and decays of particles, thanks to the bubble-chamber-like imaging performance. |
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163 | Liquid Argon TPCs are very versatile and work well with a wide particle energy range. |
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164 | Experience on such detectors has been gained within the ICARUS project \cite{Amerio:2004ze,Arneodo:2001tx}. |
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165 | \end{itemize} |
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166 | |
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167 | Three experiments are proposed to employ the above detection techniques: MEMPHYS \cite{deBellefon:2006vq} for WC, |
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168 | LENA \cite{Oberauer:2005kw, Marrodan:2006} for liquid scintillator |
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169 | and GLACIER \cite{Rubbia:2004tz,Rubbia:2004yq,Ereditato:2004ru,Ereditato:2005ru,Ereditato:2005yx} for Liquid Argon. |
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170 | In this paper we report on the study of the physics potential of the experiments and identify features of complementarity |
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171 | amongst the three techniques. |
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172 | |
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173 | Needless to say, the availability of future neutrino beams from particle accelerators |
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174 | would provide an additional bonus to the above experiments. |
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175 | Measuring oscillations with artificial neutrinos (of well known kinematical features) |
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176 | with a sufficiently long baseline would allow to accurately determine the oscillation parameters |
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177 | (in particular the mixing angle $\theta_{13}$ and the possible |
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178 | CP violating phase in the mixing matrix). |
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179 | The envisaged detectors may then be used for observing neutrinos from the future Beta Beams and Super Beams |
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180 | in the optimal energy range for each experiment. A common example |
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181 | %C Volpe 19/10/07 is a low-energy Beta Beam from CERN to MEMPHYS at Frejus, 130 km away |
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182 | is a Beta Beam from CERN to MEMPHYS at Frejus, 130 km away \cite{Campagne:2006yx}. |
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183 | High energy beams have been suggested \cite{Rubbia:2006pi}, |
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184 | favoring longer baselines of up to $O$(2000~km). |
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185 | %add C. Volpe review |
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186 | An exhaustive review on the different Beta Beam scenario can be found in the reference \cite{Volpe:2006in}. |
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187 | The ultimate Neutrino Factory facility will require a magnetized detector to fully exploit the simultaneous availability of |
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188 | neutrinos and antineutrinos. This subject is however beyond the scope of the present study. |
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189 | |
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190 | Finally, there is a possibility of (and the hope for) unexpected |
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191 | discoveries. The history of physics has shown that |
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192 | several experiments have made their glory with discoveries in research fields that were outside the original goals of the experiments. |
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193 | Just to quote an example, we can mention the Kamiokande detector, mainly designed to search for proton decay |
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194 | and actually contributing to the observation of atmospheric neutrino oscillations, to the clarification of the solar neutrino puzzle and |
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195 | to the first observation of supernova neutrinos \cite{Hirata:1987hu,Hirata:1988ad,Hirata:1989zj,Hirata:1988uy, |
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196 | Fukuda:1998mi}. |
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197 | All the three proposed experiments, thanks to their |
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198 | outstanding boost in mass and performance, will certainly provide a significant potential for surprises and unexpected discoveries. |
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199 | |
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200 | % |
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201 | \acknowledgments |
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202 | %\begin{acknowledgments} |
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203 | |
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204 | We wish to warmly acknowledge support from all the various funding agencies. We wish to thank the EU framework 6 project ILIAS for providing assistance particularly regarding underground site aspects (contract 8R113-CT-2004-506222). |
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205 | |
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206 | %\end{acknowledgments} |
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207 | \newpage |
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208 | \section*{References} |
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209 | \bibliography{campagne} |
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210 | \end{document} |
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211 | |
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212 | |
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