1. AGASA Results Masahiro Teshima for AGASA collaboration
Max-Planck-Institut für Physik, München, Germany
for AGASA collaboration

2. Cosmic Ray Energy Spectrum
AGASA Energy Spectrum P
γ3K Δ Ｎ　 π
GZK mechanism
Super GZK part.
~1/km2 century

3. AGASA Akeno Giant Air Shower Arraykm
111 Electron Det.
27 Muon Det.

4. Exposures of various experiments
Auger

5. Detector Calibration in AGASA experiment
Detector Position
Gain as a function of time
(11years data)
Survey from Airplane
ΔＸ，ΔＹ＝0.1m, ΔＺ＝0.3m
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

6. Linearity check after dismantling detectors in 2004 Feb
At Akeno Observatory Central building in 2004 Jan

7. Detector Simulation (GEANT)
Response
Detector Housing (Fe 0.4mm)
Detector Box (Fe 1.6mm)
Scintillator (50mm)
Earth (Backscattering)
Detector Simulation (GEANT)
vertical
θ = 60deg
Energy spectra of shower particles

8. Energy Determination Local density at 600m
Good energy estimator by M.Hillas
E=2.13x1020eV

9. The Highest Energy Event
2.5 x1020eV on 10 May 2001

10. Attenuation curve
S(600) vs Nch
1018eV Proton
Atmospheric depth

11. S600 Attenuation curve
20.0
19.5
19.0
18.5
18.0
Atmospheric depth

12. S600 Intrinsic fluctuation
Proton
S600 Intrinsic fluctuation
Iron

13. The Conversion
from S600 to Energy
Muon/Neutrino
Ele. Mag

14. Energy Resolution
mainly due to measurement errors (particle density measurement and core location determination) not due to shower fluctuation
30%
25%

15. Major Systematics in AGASA astro-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 ± 18%

16. Energy Spectrum by AGASA (θ<45)
11 obs. / 1.8 exp σ
5.1 x 1016 m2 s sr

17. The Energy spectrum by AGASA Red: well inside the array
(Cut the event near the boundary of array)

18. AGASA vs HiRes (astro-ph)
See new paper: Energy determination in AGASA (astro-ph/ )

19. Critical review for energy determination
Fitting the lateral distribution of shower particle density
Empirical formula (exclude errors in M.C. but limited by statistics)
no energy dependence
Linear dependence on sec(theta)
 lateral distribution obtained by Corisika

20. Lateral distribution Slope parameter eta Corskika lateral S(600)
Empirical lateral S(600)
Corskika lateral S(600)

21. S600 attenuation with recent Corsika
We are very close to S600 maximum at 1020eV
Overestimation factor
if CORSIKA is right

22. Preliminary spectra with recent Corsika
Sec(theta) =
Sec(theta) =

23. Comparison of original energy spectrum and new spectra based on Corsika
Energy shift
~10% at 1019eV
~15% at 1020eV
to lower direction
Above 1020eV
11events 
5~6 events
Spectrum becomes
more featureless
~10%
~15%

24. Auger Energy Spectrum with FD calibration
AGASA
Corsika
by Arisaka

25. Auger Energy Spectrum with MC energy by Arisaka
AGASA
Corsika
by Arisaka

26. Arrival Direction Distribution >4x1019eV zenith angle <50deg.
Isotropic in large scale  Extra-Galactic
But, Clusters in small scale (Δθ<2.5deg)
1triplet and 6 doublets (2.0 doublets are expected from random)

27. Space Angle Distribution of Arbitrary two events >4x1019eV
Normalized sigma
by Li & Ma
3.2 sigma

28. Arrival Direction Distribution >1019eV

29. Space Angle Distribution
Log E>19.6
Log E>19.4　
Log E>19.2
Log E>19.0

30. ρμ(1000) distribution

31. Summary Super GZK particles exist Small scale anisotropy of UHECR
Preliminary study with recent CORSIKA
If recent CORSIKA describes showers correctly, AGASA energy scale will shift down
by ~10% at 1019eV and by ~15% at 1020eV on average
Spectrum seems to be more featureless (in preliminary study) ??
Discrepancy between AGASA and HiRes becomes less significant
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
Re-analysis is on-going with new shower front structure (but very slow)
Chemical composition at 1019eV
Consistent with light component (P)
No gamma ray dominance, γ/all <34%