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

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

AGASA A keno G iant A ir S hower A rray operated in 1991~ Electron Det. 27 Muon Det. 0 4km

AGASA Detector Calibration in AGASA experiment Detector Gain by muons in each run Cable delay (optic fiber cable) Gain as a function of time (11years data) Accuracy of 100ps by measuring the round trip time in each run Detector Position Survey from Airplane Δ Ｘ， Δ Ｙ＝ 0.1m, Δ Ｚ＝ 0.3m Linearity as a function of time (11years data)

AGASA Detector Simulation (GEANT-3) Detector Housing (Fe 0.4mm) Detector Box (Fe 1.6mm) Scintillator (50mm) Earth (Backscattering) vertical θ = 60deg Detector Response Energy spectra of shower particles

AGASA The Highest Energy Event 2.5 x10 20 eV on 10 May 2001

AGASA Attenuation curve S(600) vs N ch eV Proton Atmospheric depth

AGASA S600 Intrinsic fluctuation Proton Iron

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

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

AGASA Major Systematics in AGASA astro-ph/ Detector Detector Absolute gain± 0.7% Detector Absolute gain± 0.7% Detector Linearity± 7% Detector Linearity± 7% Detector response(box, housing)± 5% Detector response(box, housing)± 5% Energy Estimator S(600) Interaction model, P/Fe, Height±15% Interaction model, P/Fe, Height±15% Air shower phenomenology Lateral distribution function± 7% Lateral distribution function± 7% S(600) attenuation± 5% S(600) attenuation± 5% Shower front structure ± 5% Shower front structure ± 5% Delayed particle(neutron) ± 5% Delayed particle(neutron) ± 5% Total ± 20%

AGASA Energy Spectrum by AGASA (θ<45) 11 obs. / 1.3~2.6 exp. 5.1 x m 2 s sr

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

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

AGASA Preliminary spectra with recent Corsika No difference in Models and Compositions Energy shift to lower direction ~10% at eV ~15% at eV Above eV 11events  5~6 events Featureless spectrum very close to E -3 P-SIBYLL (above eV) γ = 2.95 ±0.08 (χ 2 / NDF = 8.5/11) Fe-QGSJET (above eV) γ = 2.90 ± 0.08 (χ 2 /NDF = 8.5/11) ~10% ~15%

AGASA Arrival Direction Distribution >4x10 19 eV zenith angle 4x10 19 eV zenith angle <50deg. Isotropic in the large scale  Extra-Galactic origin But, Clusters in small scale ( Δθ< 2.5deg) 1triplet and 6 doublets (2.0 doublets are expected from random) 1triplet and 6 doublets (2.0 doublets are expected from random)

AGASA Space Angle Distribution of Arbitrary two events >4x10 19 eV Normalized sigma 3.2 sigma excess

AGASA Space Angle Distribution Log E>19.6 Log E>19.4 Log E>19.2Log E>19.0

AGASASummary Super GZK particles exist Preliminary study with recent CORSIKA Preliminary study with recent CORSIKA If we evaluate energies with the recent CORSIKA Energy scale shift down by ~10% at eV and by ~15% at eV Energy scale shift down by ~10% at eV and by ~15% at eV 11 events above eV / 1.3~2.6 expected  5~6 events / 1.0~1.9 expected 11 events above eV / 1.3~2.6 expected  5~6 events / 1.0~1.9 expected The flux difference between AGASA and HiRes becomes less significant The flux difference between AGASA and HiRes becomes less significant Small scale anisotropy of UHECR The arrival direction of UHECRs is uniform in large scale The arrival direction of UHECRs is uniform in large scale But AGASA data shows clusters, 1 triplets and 6 doublets  granularity But AGASA data shows clusters, 1 triplets and 6 doublets  granularity Source density ~10 -5 /Mpc 3 ~ density of AGNs Source density ~10 -5 /Mpc 3 ~ density of AGNs

Thank you

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