First Results from the Pierre Auger Project

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First Results from the Pierre Auger Project
A new cosmic ray observatory designed for a high
statistics study of the Highest Energy Cosmic
Rays.
Yamamoto Tokonatsu (Univ. of Chicago) for the
Pierre Auger Collaboration
Colorado, USA (in planning)
Mendoza, Argentina (construction underway)
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First Proposal in August 1992 by James W. Cronin

• Power from Solar Panel
• Network through Radio
• Absolute Timing by the GPS
• Air Shower Array of 5000 km2

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First Conceptual Design in 1992
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After 10 years
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(No Transcript)
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Plan in 1992 Area of 5000 km2 50 events /
year above 1020 eV Stand-alone Station 50ns
time resolution by GPS Micro-wave Radio
for communication Solar Battery
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The Observatory Plan
Surface Array 1600 Stations 1.5 km Spacing 3000
km2 Fluorescence Detectors 4 sites X 6
Telescopes with 440 PMTs 24 Telescopes
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Current Status (2004 summer)
gt1000 surface detector stations deployed (885
with electronics and sending triggers) Three
fluorescence buildings complete each with 6
telescopes
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Signal Map
Lateral Distribution
Shower Disc Time Structure
Zenith Angle 34 degree Energy 8 x 1019
eV
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Zenith Angle 45 degree Energy 1 x 1020
eV
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60 degrees 80 EeV
Zenith Angle 60 degree Energy 8 x 1019
eV
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72 degrees ?? EeV
Zenith Angle 72 degree Energy ???
eV
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87 degrees ?? EeV
Zenith Angle 87 degree Energy ???
eV
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Stereo-Hybrid Event
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Auger Energy Spectrum Model-Independent
Approach Use strengths from two technique

• Energy scale from the Fluorescence Telescope
  using Hybrid Events
• Calorimetric energy measurement
• No dependence on neither Interaction Model nor
  Chemical composition
• Statistics from Surface Array
• 100 duty cycle
• Huge Aperture
• Exposure from Surface Array
• No energy dependence

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Fluorescence Energy v.s. Size Parameter of the
Surface Array
Energy is estimated without air-shower
simulation. No assumption of hadronic-interactio
n model nor chemical composition.
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The First Estimation of the Energy Spectrum with
25 of a full Auger-year exposure
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Summary Spectrum above 3 EeV
aaw/Sept 2005
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Our Highest Energy Event EFDgt1.4 1020eVLanded
just outside the array, so not used in spectrum!
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Summary

• The southern site of the Pierre Auger Observatory
  is now 60 completed.
• With 25 of a full Auger-year exposure, we have
  defined our empirical spectrum analysis strategy
  and produced our first model-independent spectrum
• The Southern site will be completed in mid 2006