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AGASA

AGASA. Masahiro Teshima Max-Planck-Institut f ü r Physik, M ü nchen, Germany for AGASA collaboration. Cosmic Ray Energy Spectrum. GZK mechanism. Ｎ. P. Δ. Super GZK part. ~1/km 2 century. π. γ3K. AGASA Energy Spectrum. A keno G iant A ir S hower A rray operated in 1991~2004.

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AGASA

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

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

  3. Akeno Giant Air Shower Arrayoperated in 1991~2004 0 4km Closed in Jan 2004 111 Electron Det. 27 Muon Det.

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

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

  7. EnergyDetermination • Local density at 600m • Good energy estimator by M.Hillas E=2.1x1020eV

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

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

  10. Proton S600 Intrinsic fluctuation Iron

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

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

  13. 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%

  14. Energy Spectrum by AGASA (θ<45) 11 obs. / 1.3~2.6 exp. 5.1 x 1016 m2 s sr

  15. 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%

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

  17. Preliminary spectra with recent Corsika ~10% ~15% No difference in Models and Compositions Energy shift to lower direction ~10% at 1019eV ~15% at 1020eV Above 1020eV 11events  5~6 events Featureless spectrum very close to E-3 P-SIBYLL (above 1019eV) γ = 2.95 ±0.08 (χ2 / NDF = 8.5/11) Fe-QGSJET (above 1019eV) γ= 2.90 ± 0.08 (χ2 /NDF = 8.5/11)

  18. Arrival Direction Distribution >4x1019eVzenith 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)

  19. Space Angle Distribution of Arbitrary two events >4x1019eV Normalized sigma 3.2 sigma excess

  20. Arrival Direction Distribution >1019eV

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

  22. 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

  23. ρμ(1000) distribution

  24. 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 / 1.3~2.6 expected  5~6 events / 1.0~1.9 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

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