Size and Energy Spectra of incident cosmic radiation obtained by the MAKET - ANI surface

array on mountain Aragats. (Final results from MAKET-ANI detector)

A.Chilingarian, G.Hovsepyan

Cosmic Ray Division, Alikhanyan Physics Institute, Armenia.

MAKET-ANI detector designed to measure Extensive Air Showers (EAS) from Primary Cosmic rays (PC) with energies 105 – 108 GeV. Detector position: 3200m above see level on Mt. Aragats, Armenia. Geographic location: 40.5oN, 44.2oE

Consist – 92 plastic scintillation detector 68 with 1m2 area, and 24 – 0.09 m2.

19 of 1m2 area detectors for fast timing system.

• Two types triggers are used: » for density detectors 7 from 11

» for fast timing system 4 from 9

– Effective area for EAS collection ~900m2 for Ne >105

is the normalization factor (Hayakawa, 1969, Aseykin , 1979 )sc/chRρ

0.18

mrrρscρ

The accuracy of the reconstructed EAS core position within the collected area Seff =880m2 is less than 1 m

1.25s)(2.072s0.366C(s)

The reconstructed shower size errors (including systematic) are less than ~13% at Ne =105 and quickly decrease with the rise of shower size.

The errors of reconstructed age para-meter are less than ~9% at Ne =105.

angular accuracy not worse

•than ~1.50 for zenith θ, and for the azimuth ones Δφ ~ 50

•for the showers within 150 < θ < 450 .

,4.5s

1mr

r2s

mrr

chscRsC

2mr

eNrscρ

event { Ne, S, X0,Y0, Θ, φ}r

m =118 m

From 1997 to 2004 ~1.2 ∙ 107 shower triggers were registered. The total exposition time was ~1.42∙108 s.

Installation Stability of the operation time.

additional restrictions on the EAS triggers Ne ≥ 10 5, 0.3 < s < 1.7,

θ ≤ 46.8 o, {X0, Y

0} S

eff reduce the total number of events by an

order of magnitude to a value of ~ 1.3 ∙ 106.

MAKET-ANI measured EAS Size Spectra in comparison with KASCADE data .Both spectra for Sec uniform zenith angles interval are shown..The line indicate EAS size attenuation versus of slant depth of atmosphere.

The attenuation length by MAKET-ANI data is equal Λ=211±38 g/cm2, for KASCADE data Λ=197±13 g/cm2 and by joint analyses - Λ=194±14 g/cm2. The difference of spectral indexes before and after knee is equal Δγ = - 0.45±0.06EAS size spectra approximated by

Δγ/δδ

kneeeN

eN1γ

eN A(θ

edN

θ),edJ(N

Primary CR simulation by CORSIKA (562,QGSJet01,NKG mode) code was done. For H, He, O, Si, Fe primaries 106

events and E0≥105 GeV for each of them generated . The atmosphere depth is 700g/cm2

Yield function from simulated primaries after:

trigger conditions;

response function of installation,

is obtained.

The response of the MAKET-ANI detector on simulated “light” (p+He ) and “heavy” (Si+Fe) induced showers,

versus primary energy; shower selection criteria: N

e≥105, θ≤30o (closed symbols

), Ne≥105, 30o≤θ≤45o (open symbols)

Primary light component (p+He) measured by the MAKET-ANI detector with comparison to the results from KASCADE, EAS-TOP, HEGRA, EAS-

TOP+MACRO, TIBET and primary protons spectra approximations obtained by the single hadrons fluxes EAS-TOP and KASCADE. (All data based

on CORSIKA QGSJet01 version). The direct balloon measurements by ATIC-2 and JACEE at 102 – 105 GeV also presented.

The energy spectrum of the “heavy” nuclei group measured by the MAKET-ANI detector along with spectra from KASCADE , EAS-TOP+MACRO and ATIC-2 . The solid line is a power function

approximations

Conclusions.• From 1997 up to the end of 2004 the MAKET – ANI

experiment has taken data with exposition time of ~1.42∙108 s. The total number of the registered shower events was ~1.2∙107. A smaller sample of the data (~1.3∙106 ) with Ne ≥105 and θ ≤46.80 was used for the in-depth analysis of the LDF and size spectra. By 7.2∙105 near the vertical (θ ≤300) EAS were obtained the energy spectra of light and heavy nuclei groups.

• The obtained dependence of the shower age on shower size pointed to the weighting of the primary flux mass composition after the knee of the “all particle” spectrum;

• The size spectra show evidence of a “knee” at shower size ~106 particles. As the zenith angle enlarges, the knee position is moving to smaller sizes, according to the EAS attenuation length =211±38 g/cm2.

• The difference of the power low spectra before and after the knee is constant with high precision Δγ = 0.45 ±0.06.

• The estimated energy spectrum of the light mass group of nuclei shows a very sharp knee: ∆γ ≈ 0.9, compared to ∆γ ≈ 0.4 for the all-particle energy spectra.

• The energy spectrum of the heavy mass group of cosmic rays shows no knee in the energy interval of 1015 –1016 eV.

• The mentioned results are consistent with the nonlinear kinetic theory of CR acceleration in SNR shells