Neutrinos are
particles that interact very weakly with matter. As they are emitted in
the most violent phenomena in the Universe they could elucidate which of
these phenomena are at the origin of the cosmic radiation that impinges
continuously on the Earth’s atmosphere. Most of this radiation is composed
of charged particles, protons and nuclei that are bent by the
extragalactic magnetic fields, making it very difficult to determine their
origin.
Although no cosmic source has been
detected yet, the ANTARES sensitivity exceeds that of any previous
experiment in this hemisphere of the sky. The recording of further data
will allow the observation of the Universe with an unprecedented
sensitivity.
With scarcely one hundred days of data-taking, the
ANTARES telescope, in a configuration of only five strings, has been able
to reach a sensitivity in the southern sky higher than that of any
previous experiment. In the figure, the blue squares show the limits
obtained by ANTARES for the cosmic neutrino flux as a function of the
declination of a group of selected astrophysical sources.
|
The detection of neutrinos is a tremendous challenge that
can only be undertaken using huge detectors protected from the effects of
this cosmic radiation. ANTARES, deployed close to the French coast near
Toulon, uses the 2000 metres of water above as a natural shielding. Its
construction, has taken two years, and was completed in May 2008. Its 885
“eyes”, exceptionally sensitive photodetectors, are distributed in groups
of three along 12 strings of 450 metres of height, anchored to the sea bed.
They provide a sensitive surface equivalent to an area of four times a
soccer pitch.
The eyes of ANTARES observe the dim light trail left
by muons, charged particles very similar to electrons. These muons are
produced in the interaction of the upgoing neutrinos with the Earth’s
crust. This faint light is detected taking advantage of the darkness in
the deep sea, only broken by the sporadic light emission of some
bioluminiscent creatures. ANTARES observes the southern sky using the
terrestrial globe as filter and target. Muons are emitted in the same
direction as their parent neutrino and therefore provide the position of
their source. |
|
More.. 