The Pierre Auger Project

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The Pierre Auger Project
Claudine Colnard, Andrija Matic, Mohamed Cherif
Talai, Manuel Valverde Hermosilla
Summer School on Particle and Nuclear Astrophysics
Nijmegen, The Nederlands August 17-29, 2003
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What we "know" about Ultra High Energy cosmic Rays

Observed spectrum above eV
Doug Bergman - ICHEP2002


Evidence for Utra High Energy Cosmic Rays gt GZK
cut-off ?
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What we do not know (but would like to )

• Where does the spectrum end?
• Primary nature (composition)?
• Nucleus, proton?
• Are there gamma rays or neutrinos?
• What is the source of UHECR?
• Bottom-Up or Top-Down scenario?

Pierre Auger Observatory
A Study of The Highest Energy Cosmic Rays 1019 -
1021 eV Energy Spectrum - Direction - Composition
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Auger Philosophy
Uniform sky coverage 2 sites located in each
hemisphere Argentina, USA need high
statistics large detection surface 2?3000
km² Hybrid detector - fluorescence detector -
surface array (water Cerenkov tanks)
Good energy and direction resolution Good
sensitivity to composition
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Auger Southern Site

• Argentina Pampa Amarilla, Mendoza
• 35o S latitude
• 69o W longitude
• 1.4 km altitude
• 875 g/cm2
• Low population density (lt 0.1 / km2)
• Favorable atmospheric conditions (clouds, rain,
  light, aerosol, temperature)
• Site relatively level (mean slope lt 1)
• Suitable infrastructure and local support

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The Observatory
3000 km2 covered aperture 7400 km2 .sr
Fluorescence detectors 4 peripheral eyes (6
telescopes each) 11000 PMTs
Surface detectors 1600 Cerenkov tanks 1.5 Km
spacing 4800 PMTs

Wireless RF Communication system
65 km
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Why a hybrid detector?
The same cosmic ray shower is measured by two
independent detector systems
Cross calibration - complementary measure of the
energy and direction of the primary - allows for
redundancy cheks of interesting events - allows
to study (and reduce) systematics Increase
composition sensitivity Uniform
exposure Hadronic cascades - muon and
electromagnetic densities combined with the
longitudinal profile put constraints on the
hadronic interaction models Cost - cost per
event is lower than a stereo fluorescence
detector design
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The hybrid detector
300- 400 nm light from fluorescence of
atmospheric nitrogen

• Fluorescence Detector
• Intensity E
• Longitudinal development direction
• Duty cycle 10-15
• (moonless and cloudless nights)

• Surface Detector
• Shower size E
• Time direction
• Duty cycle 100

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The Auger Surface Detector
Water Cerenkov tank Polyethylene tank 10 m2 x
1.2 m of purified water, diffusing walls 3 PMTs
Photonis 9 Autonomous unit solar
panelbattery, GPS timing, communication
antenna modest power consumption (10 W)
Commantenna
Solar panel and electronic box
GPSantenna
Three 8 PM Tubes
Battery box
White light diffusing liner
12 m2 of de-ionized water
Plastic tank
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The FD telescope

• Schmidt optics (eliminates coma) Spherical
  mirror Rcurv 3.4 m
  2.2 m diameter diaphragm, corrector ring,
  
• 30o x 30o aperture spot size
  from spherical aberration 15 mm
• Focal surface 20 x 22 hexagonal
  PMT (Photonis XP3062) Pixel angular size
  1.5o (45 mm)

Diaphragm, UV Filter, Corrector ring
Spherical mirror
PMT camera
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Performances
1019 eV 1020 eV
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High statisitcs
1 Auger year 30 AGASA, 10 Hires years
5000 events/year E gt 1019 eV 500
events/year E gt 5x1019 eV 50
- 100 events/year E gt 1020 eV
Expected rates
Sky above after 3 years
Spectrum after 20 months
15 sources of equal densities randomly distributed
Efficiency gt 90 (Egt10 Eev)
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The Auger Collaboration

• Argentina Italy
• Australia Mexico
• Bolivia Poland
• Brazil Russia
• Czech Republic Slovenia
• Peoples Republic of China Spain
• France United Kingdom
• Germany USA
• Greece Vietnam
• 50 Institutions, gt250 Scientists

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Costs and Funding

• South 54M US
• North 46M US
• Total 100M US
• In kind contributions 80
• Detector Components
• Infrastructure (host countries)
• Common Fund 20
• Photomultiplier tubes
• Site buildings

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Status

• The Auger southern site is now under
  construction.
• 40 surface detectors over 40 km2
• 2 fluorescence telescopes (Los Leones,
  Coihueco)
• In 2003 installation and commissioning of 12 FD
  telescopes and 500 additional tanks
• Southern site to be completed by 2005
• Construction of the Auger northern detector will
  begin in 2 to 3 years.

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First giant airshower
hit 20 out of the 30 active surface detectors on
May 23rd 2002
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Summary

• Auger Project has some exciting science.
• Strong collaboration organized.
• Thirty of the surface detectors equipped with
  electronics have worked under stable conditions
  since January 2002
• More than 70 air showers detected in hybrid mode
  
• A few hundreds of events with estimated energies
  above 1 EeV (1018 eV) observed by the surface
  array alone.

Jim Cronin