Petten 29/10/99 ANTARES an underwater neutrino observatory Contents: – Introduction – Neutrino Astronomy and Physics the cosmic ray spectrum sources of neutrinos – Detection principle – Event Rates – The Antares project the Antares site deployment of a line site measurements – Conclusion Aart Heijboer

Petten 29/10/99 Introduction ANTARES =Astronomy with a Neutrino Telescope and Abyss environmental RESearch. It is a collaboration people from a.o.: CPPM, Marseilles DAPNIA-DSM-CEA, Saclay (Paris) IFIC Valencia Universities at Oxford, Sheffield, Birmingham, Mulhouse, Strasbourgh Nikhef ITEP, Moscow Oceanographic center Marseilles IFREMER which proposes to construct a large area Cherenkov detector in the deep sea, optimised for the detection of muons from high-energy astrophysical neutrinos.

Petten 29/10/99 Why detect high energy neutrinos? The Cosmic ray spectrum: 'knee' at eV events above GZK cutoff eV indication of a new region at eV Neutrinos are the only particles that are: Not deflected by magnetic fields, hence they point to their source & Not absorbed by interstellar matter and photons (GZK-cutoff), hence they allow us to identify their source look inside dense objects look further into the universe at high energies.

Petten 29/10/99 Sources of neutrinos I Accelerated charged particles: X-ray binaries Matter accreted unto a heavy central neutron star or black hole is accelerated under the influence of strong magnetic fields. Collisions with the accreting matter produce neutrinos. Supernova remnants The expanding shell of the SNR accelerates protons which interact with the matter in the shell. Active galactic nuclei (blazars) Matter accreting onto a supermassive central black hole. Often jets are produced which may contain protons which interact with surrounding photons. Gamma ray bursters Models predict highly relativistic shocks, which will accelerate protons. These interact with interstellar matter.

Petten 29/10/99 Sources of neutrinos II Atmospheric neutrinos Neutrinos from pions in the atmosphere are guaranteed to produce a signal. Checks of neutrino oscillation are possible. Decay of heavy objects: Dark matter candidates (neutralino) The neutralino may be the lightest supersymmetrical particle and is an important dark matter candidate. Neutralinos that have accumulated in the sun or earth may annihilate and produce detectable neutrino spectra Cosmological defects GUTs predict topological defects from the early universe may decay or annihilate and produce UHE neutrinos. Other exotic stuff monopoles, Q-balls, -neutrinos

Petten 29/10/99 Detection strategy Equip a natural volume of water with photomultiplier tubes positioned on strings Keep track of detector shape using acoustical system and tiltmeters. Transport (all) data to shore via electro-optical cable Charged particle v>v light Cherenkov radiation

Petten 29/10/99 Detection strategy Neutrino Muon 'Photons' Reconstructed track Trigger Select signal hits Reconstruct direction and energy

Petten 29/10/99 Event rates 8 Assume for example neutrino flux = cosmic ray flux Build a km 2 detector. But ANTARES will first build a smaller one

Petten 29/10/99 Measurement of background light Slowly varying baseline Short bursts (10 sec) up to several MHz presumably due to fish Dependent on day/night seasons current

Petten 29/10/99 Deployment of a line Release: anchor line buoy Lower the cable while adjusting the position (error = 5-10 m) Connect cables with a 'petit submarine'

Petten 29/10/99 The Antares site The location of the 0.1 km 2 detector

Petten 29/10/99 Conclusion " Building a neutrino telescope will provide a way to study the most energetic processes in the universe and the origin of cosmic rays. " Development of a 0.1 km 2 prototype has started. " Doing an experiment in a natural environment is very different from what we are used to. What will we find?

Petten 29/10/99