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Rigidity-dependent cosmic ray energy spectra in the Rigidity-dependent cosmic ray energy spectra in the knee region obtained with the GAMMA experimentknee region obtained with the GAMMA experiment

Astroparticle Physics 28/2 (2007) 169/ arXiv: 0704.320v1 [astro-ph]

4Y.Gallant, 1A.Garyaka, 2A.D.Erlykin5L.Jones, 1R.Martirosov,2N.Nikolskaya,

3J.Procureur, 1S.Ter-Antonyan

1 Yerevan Physics Institute2 Moscow Physics Institute

3 Centre d Etudes Nucleaires Bordeaux-Gradignan, 4 Universite Montpellier II

5 University of Michigan

GAMMA ExperimentGAMMA Experiment

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GAMMA FacilityGAMMA Facility

GAMMA ExperimentGAMMA Experiment

• Location: Armenia, Mt.Aragats 3200 m a.s.l.

• EAS array: 33x3 (1x1x0.05) m3+ +9 (0.3x0.3x0.05) m3

• Muon hall: 2500 g/cm2 of rock 150 (1x1x0.05)m3

• EAS data:

Nch > 5 105 (100%)

R < 25 m (50 m)

< 300

N(R<50m) > 103

E > 5 GeV

T = 6.2107 sec

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Measurement errors and particle spectra

GAMMA ExperimentGAMMA Experiment

/)( k

Ln(Nch ) 0.1, s0.05, x,y0.5-1m, 1.50

Ln(N ) 0.35-0.2 at N(R<50m)103-105

15 detectors

Particle density spectra

Single particle spectra

Ri < 50 m

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Detector response

)(

)()(

,dE

MeV1eEANch EGS

NKG

ch

ch

N

N δ

s(7m < ri < 90m)

)()()( ,E1EA de MeVsEGSNKG ss δ

CORSIKA(EGS,NKG)NA=200, A p, He, O, Fe

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A SIBYLL2.1 QGSJET01 Emin [PeV]

P 1.0·105 1.0·105 0.5

He 7.1·104 6.0·104 0.7

O 4.6·104 4.4·104 1.0

Fe 4.8·104 4.0·104 1.2

Ee, > 1 MeVE > 150 MeVMuon hall:

E > 4 GeV (e,FLUKA)

CORSIKA6.031(NKG)

GAMMA ExperimentGAMMA Experiment

Emax= 50000 PeVPeV = -1.5 < 300

R < 25m

Simulated database: WA(EA , X) {A, EA} X(Ne , Nµ , Nh , s , x0 , y0 , θ, )

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EAS Inverse Problem:EAS Inverse Problem: A

AA dEEfXEWXF )(),()(

kkZZ EEEEf /)( 1 i

2iFiFii

2 FF )]/()~

[( ,~,

3) 4D-Analysis, F(X) d4F/dNedNds dcos, nd.f.= 1640

1) Combined Analysis, nd.f.= 350

2) 2D-Analysis, F(X) d2F/dNedN , nd.f.= 240

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Primary energy spectra

kkZZ E

EEEf 1)(

0206821 .. kEE0301932 .. kEE

Rk EZE

1 = 0.0950.008 [m-2s-1sr-1TeV-1]

2 = 0.100.012

3-16 = 0.0430.007 ( O - like )

17-26 = 0.0240.004 ( Fe - like )

ER = 2500200 TV

2/nd.f. 2.0 B.Wiebel & P.Biermann, 24th ICRC (1995)

A.Lagutin et al., 29th ICRC (2005)

Results of 1-2D Combined AnalysisSIBYLL

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Verification Enlarged EAS data (R<50m)

Test of KASCADE primary energy spectra

WZ(E,X) fZ(E) dE = F(X)

Knee positions

by GAMMA EAS data

z

fp , fHe , fO=fC+fSi , fFe

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Conclusion The obtained primary energy spectra strongly depend on interaction model. The SIBYLL interaction model is more preferable. Rigidity-dependent spectra describe the EAS data at least up to E~100 PeV.All-particle primary energy spectrum slightly depends on interaction model.

The energy spectra of primary nuclei disagree with the same KASCADE data in 1-100 PeV energy range, however, the discrepancies of the all-particle energy spectra obtained by the GAMMA and KASCADE are sufficiently small (~20%).

GAMMA ExperimentGAMMA Experiment