ANTARES: Building a Deep-Sea Neutrino Telescope

Paris, December 7, 1999

CEA-CNRS Joint Press Release

Within the scope of the European experiment ANTARES (Astronomy with a Neutrino Telescope and Abyss environmental RESearch), a line to detect elementary particles, connected to the shore by 37 kilometers of electro-optical cable, was recently deployed off the coast of Marseille at a depth of 1,100 meters. The deployment of this line during the night of November 25-26, 1999, represents an important step in the building of a very large neutrino telescope. This telescope will open a new window from which to observe the Universe and will make it possible to test physical models in energy fields that are still not accessible to terrestrial accelerators. Researchers from many countries are taking part in the ANTARES experiment: in France, researchers from CEA (DSM/DAPNIA), CNRS (IN2P3 and INSU), and the Universities of the Mediterranean (Marseille), Haute-Alsace (Mulhouse), and Louis Pasteur (Strasbourg), as well as Ifremer (Institut Français de REcherche sur la MER) researchers specialized in marine environment and techniques*. Teams from Spain, the UK, the Netherlands, and Russia are also participating in this project.

Neutrinos are elementary particles. For astrophysicists, they represent an excellent means to probe the Universe more deeply and more extensively, in such a way as to complement electromagnetic radiation. Cosmic neutrinos may also constitute, at least in part, the "dark matter" in the Universe.

However, since neutrinos cannot be detected directly, they can only be observed through their interaction with matter. For the ANTARES experiment, detectors were placed deep in the sea and directed towards the sea floor. They observe neutrinos that have traveled through and interacted with the Earth. These interactions produce muons** which release streams of light in the sea water. Measuring these streams over time makes it possible to, among other things, trace the path of the neutrinos. The sea also protects the detectors from cosmic rays.

At the end of a three-year R&D program, which made it possible to validate the building of a large deep-sea neutrino telescope, today's deployment of a line 350 meters high, supporting 32 glass spheres, including eight equipped with photomultiplier tubes, is an important step in the testing of the marine technology used, the control system, and the computer processing programs. This program also involved the study of the properties of the sea environment at great depths, carried out during campaigns using CNRS boats. Tests of deep-sea connections were also performed by Nautile, an Ifremer submarine. Following a detailed analysis of the optical qualities of the water—luminous background, sedimentation and bio-fouling on the surface of the optical modules, and water transparency—the site for the ANTARES detector was chosen off the coast of Seyne sur Mer, at a depth of 2,400 meters. The Center for Particle Physics in Marseilles, one of the initiators of the project, provides local support and coordination for the project.

The ANTARES program plans to develop a detector measuring 0.1 km2 in preparation for a future telescope measuring 1 km2, which will be made up of a three-dimensional matrix covering an actual volume in the order of 1 km3. It is expected that such an arrangement will be able to detect between 100 and 2000 events (interaction of cosmic neutrinos with matter) per year. It should also enable the discovery of the main sources of high energy neutrinos and thereby open the era of neutrino astronomy.

* The experiment receives logistics and technical support from several bodies, in particular France Télécom, The Technical Centers for Naval Systems, and the DGA Technical Center for Testing Methods, and the financial support from all the municipal authorities for the towns involved.
**Particles that are similar to electrons but much heavier.

CNRS/IN2P3 Press Contacst:
Geneviève Edelheit
Tel : (33) 1 44 96 47 60
Magali Damoiseaux
Tel : (33) 4 91 82 72 28

CEA Press Contact:
Corinne Borel
Tel: (33) 1 40 56 18 35