[467] | 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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| 7 | \usepackage{rotating} |
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| 8 | |
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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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| 13 | |
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| 14 | |
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| 15 | |
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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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[468] | 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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[467] | 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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[468] | 75 | |
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| 76 | |
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| 77 | |
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[467] | 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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