AGASA ResultsAGASA Results

Masahiro TeshimaMasahiro TeshimaMax-Planck-Institut fMax-Planck-Institut füür Physik, Mr Physik, Müünchen, Germanynchen, Germany

for AGASA collaborationfor AGASA collaboration

AGASA

Cosmic Ray Energy SpectrumCosmic Ray Energy Spectrum

P

γ3K

ΔＮ　

π

GZK mechanism

AGASA Energy Spectrum

Super GZK part.~1/km2 century

AGASA AGASAAGASAAkeno Giant Air Shower ArrayAkeno Giant Air Shower Array

111 Electron Det.27 Muon Det.

0 4km

AGASA Exposures of various Exposures of various experimentsexperiments

Auger

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 AirplaneΔＸ， ΔＹ＝ 0.1m, ΔＺ＝ 0.3m

Linearity as a function of time(11years data)

AGASA Linearity check after dismantling detectors in 2004 Feb

At Akeno Observatory Central building in 2004 Jan

AGASAD

ete

ctor

Sim

ula

tion

(GEA

NT)

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

EnergyEnergy 　　 DeterminationDetermination

Local density at 600mLocal density at 600m Good energy estimator by M.HillasGood energy estimator by M.Hillas

E=2.13x1020eV

AGASA

The Highest Energy Event The Highest Energy Event 2.5 x102.5 x102020eV on 10 May 2001eV on 10 May 2001

AGASA

Attenuation curveAttenuation curveS(600) vs Nch

1018eV Proton

Atmospheric depth

AGASA

S600 Attenuation curveS600 Attenuation curve

Atmospheric depth

20.0

19.5

19.0

18.5

18.0

AGASA

S6

00

Intr

insi

c fluct

uati

on

Proton

Iron

AGASA The Conversion from S600 to Energy

Muon/Neutrino

Ele. Mag

AGASA

Energy ResolutionEnergy Resolution

30% 25%

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

AGASA Major Systematics in AGASAMajor Systematics in AGASAastro-ph/0209422astro-ph/0209422

DetectorDetector Detector Absolute gainDetector Absolute gain ±± 0.7% 0.7% Detector LinearityDetector Linearity ±± 7% 7% Detector response(box, housing)Detector response(box, housing) ±± 5% 5%

Energy Estimator S(600)Energy Estimator S(600) Interaction model, P/Fe, HeightInteraction model, P/Fe, Height ±±15%15%

Air shower phenomenologyAir shower phenomenology Lateral distribution functionLateral distribution function ±± 7% 7% S(600) attenuationS(600) attenuation ±± 5% 5% Shower front structureShower front structure ±± 5% 5% Delayed particle(neutron)Delayed particle(neutron) ±± 5% 5%

TotalTotal ±± 18% 18%

AGASA

Energy Spectrum by AGASA (θ<45)

11 obs. / 1.8 exp. 4.2σ

5.1 x 1016 m2 s sr

AGASA The Energy spectrum by AGASA Red: well inside the array

(Cut the event near the boundary of array)

AGASA

AGASA vs HiRes (astro-ph)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)

AGASA Critical review for energy Critical review for energy determinationdetermination

Fitting the lateral distribution of shower parFitting the lateral distribution of shower particle densityticle density Empirical formula (exclude errors in M.C. but liEmpirical formula (exclude errors in M.C. but li

mited by statistics)mited by statistics)no energy dependenceno energy dependenceLinear dependence on sec(theta)Linear dependence on sec(theta)

lateral distribution obtained by Corisikalateral distribution obtained by Corisika

AGASA

Lateral distributionLateral distribution

Empirical lateral S(600)

Cors

kika

late

ral S

(600

)

Slope parameter eta

AGASA S600 attenuation with recent CorS600 attenuation with recent Corsikasika

Overestimation factor if CORSIKA is right

We are very close to S600 maximum at 1020eV

AGASA Preliminary spectra with recent CoPreliminary spectra with recent Corsikarsika

Sec(theta) =1.0 - 1.2 Sec(theta) =1.2 - 1.4

AGASAComparison of original energy spectrum and new spectra Comparison of original energy spectrum and new spectra

based on Corsikabased on Corsika

Energy shift~10% at 1019eV~15% at 1020eVto lower direction

Above 1020eV11events 5~6 events

Spectrum becomes more featureless

~10% ~15%

AGASA Auger Energy SpectrumAuger Energy Spectrumwith FD calibrationwith FD calibration

AGASACorsika

by Arisaka

AGASA Auger Energy SpectrumAuger Energy Spectrumwith MC energy by Arisakawith MC energy by Arisaka

AGASACorsika

by Arisaka

AGASAArrival Direction Distribution >4x10Arrival Direction Distribution >4x101919eVeV

zenith angle <50deg.zenith angle <50deg.

Isotropic in large scale Isotropic in large scale Extra-Galactic Extra-GalacticBut, Clusters in small scale (But, Clusters in small scale (ΔθΔθ<<2.5deg)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 Space Angle Distribution of Arbitrary two events >4x10two events >4x101919eVeV

Normalized sigmaby Li & Ma

3.2 sigma

AGASA

Arrival Direction Distribution >10Arrival Direction Distribution >101919eVeV

AGASA

Space Angle DistributionSpace Angle Distribution

Log E>19.6 Log E>19.4　

Log E>19.2 Log E>19.0

AGASA

ρρμμ(1000) distribution(1000) distribution

AGASA

SummarySummarySuper GZK particles existSuper GZK particles exist

Preliminary study with recent CORSIKAPreliminary study with recent CORSIKAIf recent CORSIKA describes showers correctly, AGASA energy scaIf recent CORSIKA describes showers correctly, AGASA energy scale will shift down le will shift down

by ~10% at 10by ~10% at 101919eV and by ~15% at 10eV and by ~15% at 102020eV on averageeV on averageSpectrum seems to be more featureless (in preliminary study) ?? Spectrum seems to be more featureless (in preliminary study) ?? Discrepancy between AGASA and HiRes becomes less significantDiscrepancy between AGASA and HiRes becomes less significant

Small scale anisotropy of UHECRSmall scale anisotropy of UHECR The arrival direction of UHECRs is uniform in large scaleThe arrival direction of UHECRs is uniform in large scale But AGASA data shows clusters, 1 triplets and 6 doublets But AGASA data shows clusters, 1 triplets and 6 doublets gra gra

nularitynularity Source density ~10Source density ~10-5-5/Mpc/Mpc3 3 ~ density of AGNs ~ density of AGNs Re-analysis is on-going with new shower front structure (but verRe-analysis is on-going with new shower front structure (but ver

y slow)y slow)

Chemical composition at 10Chemical composition at 101919eVeV Consistent with light component (P)Consistent with light component (P) No gamma ray dominance, No gamma ray dominance, γγ/all/all <34% <34%