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Scientific Report 2007-2009<br />
Particle physics<br />
P31. ANTARES: a Čerenkov Neutrino deep-sea detector.<br />
The undisputed galactic origin of cosmic rays at energies<br />
below the so-called knee implies an existence of<br />
a non-thermal population of galactic sources which effectively<br />
accelerate protons and nuclei to TeV-PeV energies.<br />
The distinct signatures of these cosmic accelerators<br />
are high energy neutrinos and gamma rays produced<br />
through hadronic interactions with ambient gas or photoproduction<br />
on intense photon fields near the source.<br />
While gamma rays can be produced also by directly accelerated<br />
electrons, high-energy neutrinos provide unambiguous<br />
and unique information on the sites of the cosmic<br />
accelerators and hadronic nature of the accelerated<br />
particles. The original idea of a neutrino telescope based<br />
on the detection of the secondary particles produced in<br />
neutrino interactions is attributed to Markov [1] who<br />
invoked the concept in the 1950’s. Events reconstruction<br />
is possible through the Čerenkov light induced by<br />
the path of the interaction products in transparent media.<br />
The Antares neutrino telescope, operating at 2.5 km<br />
depth in the Mediterranean Sea, 40 km off the Toulon<br />
shore, represents the world’s largest operational underwater<br />
neutrino telescope, optimized for the detection of<br />
Čerenkov light produced by neutrino-induced muons. It<br />
is equipped with 885 optical sensors arranged on 12 flexible<br />
lines (Figure 1). Each line comprises up to 2 detection<br />
storeys each equipped with three downward-looking<br />
10-inch photo-multipliers (PMTs), orientated at 45 ◦ to<br />
the line axis. The lines are maintained vertical by a<br />
buoy at the top of the 450 m long line. The spacing<br />
between storeys in 14.5 m and the lines are spaced by<br />
60-70 m. An acoustic positioning system provides realtime<br />
location of the detector elements to a precision of<br />
a few centimeters. Antares is taking data in its full 12<br />
lines configuration since May 2008.<br />
cosmos; among them are Supernova Remnants, Pulsars<br />
and Microquasars in the Galaxy. Possible extragalactic<br />
sources include Active Galactic Nuclei and γ −ray burst<br />
emitters. For such processes the neutrino energy scale is<br />
10 12 to 10 16 eV . Another important objective of neutrino<br />
telescopes like ANTARES is the search for dark matter<br />
in the form of WIMPs (Weakly Interacting Massive Particles).<br />
As an example in the case of supersymmetric<br />
theories with R-parity conservation, the relic neutralinos<br />
from the Big-Bang are predicted to concentrate in<br />
massive bodies such as the centres of the Earth, the Sun<br />
or the Galaxy. At these sites neutralino annihilations,<br />
and the subsequent decays of the resulting particles, may<br />
yield neutrinos with energies up to 10 10 - 10 12 eV . Additionally<br />
the study of the diffuse neutrino flux, originating<br />
from sources that cannot be individually resolved or from<br />
interactions of cosmic rays with intergalactic matter or<br />
radiation, may yield important cosmological clues. Such<br />
measurements would be significant for neutrino energies<br />
in excess of 10 15 eV . The apparatus is well performing<br />
[2], [3], [4] and already allowed to reconstruct neutrino<br />
events (Figure 2).<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0 180° −180°<br />
−20<br />
−40<br />
−60<br />
−80<br />
−100<br />
−90°<br />
−200 −150 −100 −50 0 50 100 150 200<br />
90°<br />
ANTARES − Preliminary<br />
Figure 2: Sky map, in equatorial coordinates, of 750 neutrino<br />
candidates selected out of the 2007-2008 ANTARES data.<br />
We participated to the construction of the detector<br />
and to data analysis with a special interest for the<br />
detection of ”Sources in the Super-Galactic Plane”.<br />
References<br />
1. M. A. Markov, in Proc. Int. Conf. on High Energy<br />
Physics, Rochester, U.S.A., 1960 183, (1960).<br />
2. J. A. Aguilar et al., Astropart. Phys., 33, 86,90 (2010).<br />
3. M. Ageron et al., Astropart. Phys., 33, 277,283 (2009).<br />
4. J. A. Aguilar et al., NIM-A 581, 695-708 (2007).<br />
Authors<br />
F. Ameli, A. Capone, T. Chiarusi, G. De Bonis, F. Lucarelli,<br />
R. Masullo, F. Simeone, M. Vecchi<br />
Figure 1: The layout of the completed ANTARES detector.<br />
www.roma1.infn.it/people/capone/AHEN/index.htm<br />
The main goal of Antares is the search of high energy<br />
neutrinos from astrophysical point or transient sources.<br />
There are numerous candidate neutrino sources in the<br />
<strong>Sapienza</strong> Università di Roma 138 Dipartimento di Fisica