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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

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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.

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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.

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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.

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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

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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

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Detection strategy

Neutrino

Muon

'Photons'

Reconstructed track

•Trigger•Select signal hits•Reconstruct direction and energy

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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

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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

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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

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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?

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