AGASA Masahiro Teshima MaxPlanckInstitut fr Physik Mnchen Germany

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

AGASA Cosmic Ray Energy Spectrum AGASA Energy Spectrum P γ 3 K Δ Ｎ　 π GZK mechanism Super GZK part. ~1/km 2 century

AGASA Akeno Giant Air Shower Array operated in 1991~2004 Closed in Jan 2004 111 Electron Det. 27 Muon Det. 0 4 km

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

AGASA Detector Calibration in AGASA experiment Detector Position Survey from Airplane ΔＸ，ΔＹ＝ 0. 1 m, ΔＺ＝ 0. 3 m Cable delay Gain as a function of time (11 years data) (optic fiber cable) Accuracy of 100 ps by measuring the round trip time in each run Detector Gain by muons in each run Linearity as a function of time (11 years data)

Detector Simulation (GEANT-3) AGASA Detector Housing (Fe 0. 4 mm) Detector Box (Fe 1. 6 mm) Scintillator (50 mm) Earth (Backscattering) Detector Response vertical Energy spectra of shower particles θ = 60 deg

AGASA Energy　Determination Local density at 600 m n Good energy estimator by M. Hillas E=2. 1 x 1020 e. V

AGASA The Highest Energy Event 2. 5 x 1020 e. V on 10 May 2001

AGASA Attenuation curve S(600) vs Nch 1018 e. V Proton Atmospheric depth

S 600 Intrinsic fluctuation AGASA Proton Iron

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

AGASA The Conversion from S 600 to Energy Muon/Neutrino Ele. Mag

AGASA Major Systematics in AGASA astro-ph/0209422 Detector n Detector Absolute gain n Detector Linearity n Detector response(box, housing) Energy Estimator S(600) n Interaction model, P/Fe, Height Air shower phenomenology n Lateral distribution function n S(600) attenuation n Shower front structure n Delayed particle(neutron) Total ± 0. 7% ± 5% ± 15% ± ± 7% 5% 5% 5% ± 20%

AGASA Energy Spectrum by AGASA (θ<45) 11 obs. / 1. 3~2. 6 exp. 5. 1 x 1016 m 2 s sr

Critical review of energy estimation and spectrum AGASA Acceptance of Array n n n 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 n n n Lateral distribution determined by experiment Lateral distribution estimated by Corsika M. C. No difference Attenuation of S(600) n n n Attenuation curve determined by experiment Attenuation curve estimated by Corsika M. C. There is systematic difference of 10 -20%

AGASA S 600 attenuation with recent Corsika We are very close to S 600 maximum at 1020 e. V Overestimation factor compared with Corsika

AGASA Preliminary spectra with recent Corsika No difference in Models and Compositions ~15% Energy shift to lower direction ~10% at 1019 e. V ~15% at 1020 e. V ~10% Above 1020 e. V 11 events 5~6 events Featureless spectrum very close to E-3 P-SIBYLL (above 1019 e. V) γ = 2. 95 ± 0. 08 (χ2 / NDF = 8. 5/11) Fe-QGSJET (above 1019 e. V) γ = 2. 90 ± 0. 08 (χ2 /NDF = 8. 5/11)

AGASA Arrival Direction Distribution >4 x 1019 e. V zenith angle <50 deg. Isotropic in the large scale Extra-Galactic origin But, Clusters in small scale (Δθ<2. 5 deg) n 1 triplet and 6 doublets (2. 0 doublets are expected from random)

AGASA Space Angle Distribution of Arbitrary two events >4 x 1019 e. V Normalized sigma 3. 2 sigma excess

AGASA Arrival Direction Distribution >1019 e. V

Space Angle Distribution AGASA Log E>19. 0 Log E>19. 2 Log E>19. 4　 Log E>19. 6

AGASA Triplet + Hi. Res These events are on the supergalactic plane Arp 299: 40 Mpc Colliding galaxy NGC 3610: 33 Mpc Merger Remnant NGC 3613: 36 Mpc AGN Remnant MAGIC made the observation of these objects, Results will come in ICRC 07

AGASA ρμ(1000) distribution

AGASA Summary Super GZK particles n Preliminary study with recent CORSIKA If we evaluate energies with the recent CORSIKA n n Energy scale shift down by ~10% at 1019 e. V and by ~15% at 1020 e. V 11 events above 1020 e. V / 1. 3~2. 6 expected 5~6 events / 1. 0~1. 9 expected Small scale anisotropy of UHECR n n n 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/Mpc 3 ~ density of AGNs