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Petten 29/10/99
ANTARESan 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
IntroductionANTARES =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 1015 eV• events above GZK cutoff
5.1019 eV• indication of a new region
at 1020 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 binariesMatter 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 remnantsThe 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 burstersModels predict highly relativistic shocks, which will accelerate protons.
These interact with interstellar matter.
Petten 29/10/99
Sources of neutrinos II
• Atmospheric neutrinosNeutrinos 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 defectsGUTs predict topological defects from the early universe may decay or
annihilate and produce UHE neutrinos.
• Other exotic stuffmonopoles, 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 particlev>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
N
R
At
8
E Flux (km2 year) - 1
Pdet N(km2 year) - 1
TeV 1013 10- 6 107
PeV 106 10- 3 103
EeV 1 0.1 0.1
Assume for example neutrino flux = cosmic ray flux
Build a km2 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'
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The Antares site
The location of the 0.1 km2 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 km2 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