News from Deep-sea

The Antares project aims to build a deep-sea Cherenkov Telescope for High Energy Neutrino Astronomy located in the Mediterranean Sea. The experiment, currently in the construction phase, has recently achieved an important milestone : the operation of a prototype line and of a line with monitoring instruments. These deployments allowed a thorough understanding of environmental parameters. http://antares.in2p3.fr 1 2 Frontier Science 2004, Physics and Astrophysics in Space 1 High Energy Neutrinos and AstroParticle Physics The advantage of using neutrinos as new messengers lies on their weak interaction cross-section: unlike protons or gammas, they provide a cosmological-range, unaltered information from the very heart of their sources. The drawback is that their detection requires a huge detection volume. In all those aspects, neutrinos are comparable to gravitational waves (GW). This comparison applies also to the sources of high energy neutrinos themselves. Such sources, either galactic or extra-galactic, are compact objects, involving relativistic movements of masses and particles, all necessary ingredients to have an efficient gravitational wave emission (see section 2.3). Most of those sources have already been extensively observed in γ: supernovae and their remnants, pulsars, microquasars and AGNs, gamma-ray bursters. The main question is to know whether or not those photons are produced by electrons via inverse compton/synchrotron emission or by protons/nuclei via production of neutral and charged pions, which decay to produce photons and neutrinos. 2 The Antares Neutrino Telescope Antares can be seen as a fixed target experiment: a cosmic neutrino interacts in the Earth and produces a muon that propagates in sea water. The Cherenkov light emitted by the muon is detected by an array of photomultipliers arranged in strings, able to reconstruct the energy and direction of the incident muon/neutrino. The main physical backgrounds are twoflod. Atmospheric muons, produced in the upper atmosphere by the interaction of cosmic rays, can be discarded because of their downward direction. Atmospheric neutrinos on the other hand are more delicate to identify: produced on the other side of the Earth, they have exactly the same signature as the cosmic signal Antares awaits for. They also represent a powerful calibration tool. 2.1 The Antares Collaboration and the detector The goal of the European collaboration Antares [1] is thus to build an underwater telescope dedicated to high energy neutrinos. Around 20 particle physics laboratories, astrophysics and oceanography institutes are taking part in the project. The selected site is in the Mediterranean Sea, 40 km from Toulon (Southern France), at a depth of 2500m. The detector consists in twelve lines, each one being composed of 25 storeys. On each storey, 3 photomultipliers are looking downward, to be sensitive to upward-going muons only. The layout of the detector is described in Figure 1. Th. Pradier Antares : Status & Milestones 3 Junction Box 300m Compass, Tiltmeter, Electronics