The Cosmic ray energy spectrum above 3 x 10**18-eV measured by the Akeno Giant Air Shower Array
Aug, 1994
29 pages
Published in:
- Astropart.Phys. 3 (1995) 105-124
Report number:
- ICRR-325-94-20
Experiments:
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Abstract: (Elsevier)
We report the first result on the cosmic ray energy spectrum above 3 × 10 18 eV measured by the Akeno Giant Air Shower Array (AGASA) from July 1990 to February 1994. The analysis method and the energy resolution of the AGASA experiment are described in some detail. The flattening of the spectrum around 10 19 eV (ankle) is observed with a significance of 2.9σ. If we express the differential energy spectrum of cosmic rays of energy E (in eV) with an ankle energy E a as J(E) = κ( E E a ) −γ m −2 s −1 sr −1 eV −1 , γ for 10 18.5 eV ≤ E ≤ E a is in good agreement with that from the previous experiment and is 3.2 ± 0.1. The slope γ above E a depends strongly on the value E a . For the case E a = 10 19 eV, κ = (2.3 −0.2 +0.1 ) × 10 −33 and γ = 2.3 −0.3 +0.5 for 10 19 eV ≤ E ≤ 10 20 eV. If E a = 10 18.8 eV, then κ = (1.0 ± 0.1) × 10 −32 and γ = 2.7 −0.4 +0.2 for 10 18.8 eV ≤ E ≤10 20 eV, after correcting for both the statistical error and the energy resolution of the present experiment. If we interpret the present results assuming an extragalactic origin for cosmic rays above 10 19 eV, the observed data is consistent with either a homogeneous and isotropic distribution of sources or with localized sources at redshift of greater than ∼ 0.1. A (1.7–2.6) × 10 20 eV event was observed on December 3, 1993 from the direction of l = 131° and b = −41°. This shower energy is a factor 3 larger than the second highest energy event.- cosmic radiation: energy spectrum
- energy spectrum: cosmic radiation
- energy spectrum: slope
- slope: energy spectrum
- showers: air
- cosmic radiation: primary
- cosmic radiation: particle source
- energy resolution
- shower detector: experimental results
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