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Scientific Report 2007-2009
Particle physics
P32. High Energy Neutrino astronomy in the Mediterranean Sea,
NEMO and KM3NeT projects.
The major scientific objective of this research is the
study of the Universe by means of the observation of
High Energy Neutrinos. Neutrinos are produced as
secondary products of interactions of the accelerated
charged cosmic rays in all models of cosmic sources of
high-energy radiation. To have adequate sensitivity for
the expected fluxes of astrophysical neutrinos, detectors
with very large volumes, of the order of a km 3 , are required.
The construction of a km 3 -scale Neutrino Telescope
in the Mediterranean Sea is the goal of the European
consortium KM3NeT of which we are between the
promoters [1]. The Mediterranean Sea provides the large
target mass necessary to enhance the detection rate and
the transparency of its water makes it ideal to house a
large array of light sensors to detect this Čerenkov light;
it’s geographic location is ideal since the region of the sky
observed includes the bulk of the Galaxy. We did search
and characterize the optimal deep-sea sites [2] for the detector
installation and participated to the development
of key technologies for the km 3 underwater telescope.
As a prototype of the km 3 Čerenkov neutrino detector
NEMO Collaboration did construct, install and operate
a four floors detector (Figure 1) at 2100m depths close
to Catania port.
Figure 2: NEMO: reconstruction of a downgoing atmospheric
muon track.
as foreseen if assuming the interaction between high
energy protons and the microwave cosmic background
radiation (the so called GZK effect). Neutrinos resulting
from such interactions would have energies in the range
10 17 − 10 21 eV and their flux would be so faint that
they could not be revealed by a Čerenkov Neutrino
Telescope with a km 2 effective area. High-energy
neutrino interactions can originate high-energy showers
that deposit their energy in a limited volume of water.
The shower energy is released in the medium through
a thermal-acoustic mechanism that induces a local
enhancement of the temperature. The consequent fast
expansion of the heated volume of water generates a
pressure wave which is detectable as an acoustic signal.
We are developing technologies to exploit the acoustic
detection, in deep-sea water, of UHE neutrinos [4].
References
1. http://www.km3net.org/
2. A. Capone et al., NIM-A 487, 423-434 (2002), G.
Riccobene et al. Astropart. Phys. 27, 1-9 (2007)
3. F. Ameli et al., IEEE Transactions on Nuclear Science
55, 233-240 (2008).
4. A. Capone and G. De Bonis, International Journal of
Modern Physics A, 21, (2006).
Figure 1: Scheme of the four floors prototype tower of the
NEMO Phase-1 project.
The data analysis confirmed the expectations for detector
resolutions and muon rates (Figure 2). The Roma
group also developed, constructed and tested the whole
electronics system for data acquisition and transmission
[3] to the on-shore laboratory of all PMTs signals.
Recent AUGER results show that the spectrum of
Ultra High Energy cosmic rays (E > 10 19 eV ) behaves
Authors
F.Ameli, M.Bonori, A.Capone, T.Chiarusi, G.DeBonis,
A.Lonardo, F.Lucarelli, R.Masullo, F.Simeone, M.Vecchi,
P.Vicini
www.roma1.infn.it/people/capone/AHEN/index.htm
Sapienza Università di Roma 139 Dipartimento di Fisica