AGASA

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AGASA

• Masahiro Teshima
• Max-Planck-Institut für Physik, München, Germany
• for AGASA collaboration

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Cosmic Ray Energy Spectrum
AGASA Energy Spectrum
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Akeno Giant Air Shower Arrayoperated in 19912004
Closed in Jan 2004
111 Electron Det. 27 Muon Det.
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Linearity check after dismantling detectors in
2004 Feb
At Akeno Observatory Central building in 2004 Jan
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Detector Calibration in AGASA experiment
Gain as a function of time (11years data)
Detector Position
Survey from Airplane ?X,?Y0.1m, ?Z0.3m
Cable delay (optic fiber cable)
Accuracy of 100ps by measuring the round trip
time in each run
Linearity as a function of time (11years data)
Detector Gain by muons in each run
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Detector Housing (Fe 0.4mm) Detector Box (Fe
1.6mm) Scintillator (50mm) Earth (Backscattering)
Detector Simulation (GEANT-3)
Energy spectra of shower particles
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Energy Determination

• Local density at 600m
• Good energy estimator by M.Hillas

E2.1x1020eV
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The Highest Energy Event
2.5 x1020eV on 10 May 2001
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Attenuation curve
S(600) vs Nch
1018eV Proton
Atmospheric depth
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Proton
S600 Intrinsic fluctuation
Iron
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Energy Resolution
mainly due to measurement errors (particle
density measurement and core location
determination)not due to shower fluctuation
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The Conversion from S600 to Energy
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Major Systematics in AGASAastro-ph/0209422

• Detector
• Detector Absolute gain 0.7
• Detector Linearity 7
• Detector response(box, housing) 5
• Energy Estimator S(600)
• Interaction model, P/Fe, Height 15
• Air shower phenomenology
• Lateral distribution function 7
• S(600) attenuation 5
• Shower front structure 5
• Delayed particle(neutron) 5
• Total 20

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Energy Spectrum by AGASA (?lt45)
11 obs. / 1.32.6 exp.
5.1 x 1016 m2 s sr
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Critical review of energy estimation and spectrum

• Acceptance of Array
• AGASA fast simulation (based on empirical formula
  and toy simulation)
• Based on CORSIKA M.C.
• Essentially acceptance is saturated ? No
  difference
• Lateral distribution of showers
• Lateral distribution determined by experiment
• Lateral distribution estimated by Corsika M.C.
• ? No difference
• Attenuation of S(600)
• Attenuation curve determined by experiment
• Attenuation curve estimated by Corsika M.C.
• There is systematic difference of 10-20

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S600 attenuation with recent Corsika
We are very close to S600 maximum at 1020eV
Overestimation factor compared with Corsika
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Preliminary spectra with recent Corsika

• No difference in Models and
• Compositions
• Energy shift to lower direction
• 10 at 1019eV
• 15 at 1020eV
• Above 1020eV
• 11events ? 56 events
• Featureless spectrum
• very close to E-3
• P-SIBYLL (above 1019eV)
• ? 2.95 0.08
• (?2 / NDF 8.5/11)
• Fe-QGSJET (above 1019eV)
• ? 2.90 0.08

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Arrival Direction Distribution gt4x1019eVzenith
angle lt50deg.

• Isotropic in the large scale ? Extra-Galactic
  origin
• But, Clusters in small scale (??lt2.5deg)
• 1triplet and 6 doublets (2.0 doublets are
  expected from random)

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Space Angle Distribution of Arbitrary two events
gt4x1019eV
Normalized sigma 3.2 sigma excess
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Arrival Direction Distribution gt1019eV
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Space Angle Distribution
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AGASA Triplet HiRes
These events are on the supergalactic
plane Arp299 40Mpc Colliding galaxy NGC3610
33Mpc Merger Remnant NGC3613 36Mpc AGN
Remnant MAGIC made the observation of these
objects, Results will come in ICRC07
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?µ(1000) distribution
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Summary

• Super GZK particles
• Preliminary study with recent CORSIKA
• If we evaluate energies with the recent CORSIKA
• Energy scale shift down by 10 at 1019eV and by
  15 at 1020eV
• 11 events above 1020eV / 1.32.6 expected ?
  56 events / 1.01.9 expected
• Small scale anisotropy of UHECR
• The arrival direction of UHECRs is uniform in
  large scale
• But AGASA data shows clusters, 1 triplets and 6
  doublets ? granularity
• Source density 10-5/Mpc3 density of AGNs