AGASA Results

Max-Planck-Institut für Physik, München, Germany

Masahiro Teshimafor AGASA collaboration

at 3rd Int. Workshop on UHECR, Univ. Leeds

Cosmic Ray Energy Spectrum

P

γ3K

ΔＮ　

π

GZK mechanism

AGASA Energy Spectrum

Super GZK part.~1/km2 century

AGASAAkeno Giant Air Shower

Array

111 Electron Det.27 Muon Det.

0 4km

Exposure in ICRC2003

Auger

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 AirplaneΔＸ， ΔＹ＝ 0.1m, ΔＺ＝ 0.3m

Linearity as a function of time(11years data)

Detector Simulation (GEANT)

Detector Housing (Fe 0.4mm)Detector Box (Fe 1.6mm)Scintillator (50mm)Earth (Backscattering)

vertical θ = 60deg

Detector Response

Energy spectra of shower particles

Linearity check

Energy　 DeterminationLocal density at 600mGood energy estimator by M.Hillas

E=2.13x1020eV, E >= 1.6x1020eV

Third Highest event97/03/30 150EeV

40 detecters were hit

The Highest Energy Event (2.46 x1020eV, E>1.6x1020eV)

on 10 May 2001

Attenuation curve S(600) vs Nch

1018eV Proton

Atmospheric depth

S600 Attenuation curve

　 0-45°

　 0-60°

Atmospheric depth

20.0

19.5

19.0

18.5

18.0

S600 Intrinsic fluctuation for

proton and iron

Proton

Iron

The Conversion from S600 to Energy

Muon/Neutrino

Ele. Mag

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 ± 18%

Energy Resolution

30% 25%

mainly due to measurement errors (particle density measurement and core location determination)not due to shower fluctuation

Energy Spectrum by AGASA (θ<45)

11 obs. / 1.8 exp. 4.2σ

5.1 x 1016 m2 s sr

The Energy spectrum by AGASA Red: well inside the array

(Cut the event near the boundary of array)

AGASA vs HiRes (astro-ph)See new paper: Energy determination in AGASA (astro-ph/0209422)See new paper: Energy determination in AGASA (astro-ph/0209422)

Recent spectra (AGASA vs. HiRes@Tsukuba ICRC)

~2.5 sigma discrepancy between AGASA & HiRes

Energy scale difference by 25% vs. HiRes-stereo

vs. HiRes-I

vs. HiRes-II

Arrival Direction Distribution >4x1019eVzenith angle <50deg.

Isotropic in large scale Extra-GalacticBut, Clusters in small scale (Δθ<2.5deg) 1triplet and 6 doublets (2.0 doublets are expected from random) One doublet triplet(>3.9x1019eV) and a new doublet(<2.6deg)

Space Angle Distribution of Arbitrary two events >4x1019eV

Normalized sigmaby Li & Ma

3.2 sigma

Arrival Direction Distribution >1019eV

Space Angle Distribution

Log E>19.6 Log E>19.4　

Log E>19.2 Log E>19.0

Energy spectrum of Cluster events∝E -1.8+-0.3

Cluster Component

ρμ(1000) distribution

Akeno 1km2 (A1): Hayashida et al. ’95 Haverah Park (HP): Ave et al. ’03Volcano Ranch (VR): Dova et al. (ICRC ‘03)HiRes (HiRes): Archbold et al. (ICRC ‘03)

A1: PRELIMINARY

1017.5eV – 1019eV (Akeno 1km2 array)

Gradual lightening

Above 1019eV (AGASA)

Fe frac.: <40% (@90% CL)

Chemical composition study by muons(p+Fe composition assumption; AIRES+QGSJET)

(PRELIMINARY)

Limits on gamma-ray fraction

Gamma-ray fraction upper limits (@90%CL)

34% (>1019eV)(/p<0.45)

56% (>1019.5eV)(/p<1.27)

to observed events Topological defects (Sigl et al. ‘01) (Mx=1016[eV]; flux normalised@1020eV )Z-burst model(Sigl et al. ‘01)(Flux normalised@1020eV)

SHDM-model (Berezinski et al. ‘98) (Mx=1014[eV]; flux normalised@1019eV )

Assuming 2-comp. (p+gamma-ray) primaries

SummarySuper GZK particles exist AGASA HiRes difference is small, 　 problem; FLUX Origin of UHECR (Possible scenario)

Fe Primary – most economical scenario – but not likely Decay of Heavy Relics in our Halo (WIMPZILLA) Violation of Special Relativity AGNs, GRBs or other astronomical objects Over density?

Small scale anisotropy of UHECR AGASA data shows clusters, 1 triplets 6 doublets Source density ~10-5/Mpc3 ~ density of AGNs

Chemical composition at 1019eV Consistent with light component (P) No gamma ray dominance, γ/all <34%

New Projects for UHECRs

Golden Time for UHECRs