On the Global Anisotropy of Cosmic Ray Data above 4 × 10 19 eV
The distribution of arrival directions of ultra-high energy cosmic rays may yield clues to their mysterious origin. We introduce a method of invariant statistics to analyze cosmic ray data which eliminates coordinate-dependent artifacts. When combined with maximum likelihood analysis, the method is...
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| Format: | Text |
| Language: | English |
| Published: |
2001
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.258.499 http://arxiv.org/pdf/astro-ph/0110045v1.pdf |
| Summary: | The distribution of arrival directions of ultra-high energy cosmic rays may yield clues to their mysterious origin. We introduce a method of invariant statistics to analyze cosmic ray data which eliminates coordinate-dependent artifacts. When combined with maximum likelihood analysis, the method is capable of quantifying deviations of the distribution from isotropy with high reliability. We test our method against published AGASA events with energies above 4×10 19 eV. Angular cuts from observational limitations are taken into account. A model based on the Fisher distribution reveals the rotation of the Earth with the axis ˆn along the direction (5 h 53.36 m, 85.78 ◦) in (RA, DEC) coordinates, which is within 5 ◦ of the equatorial north pole. Global anisotropy of the data, if any, hinges on finer understanding of detector acceptance than what is available from the published literature. Introduction: A puzzle has existed for more than 30 years regarding cosmic ray events with energies exceeding 4 × 10 19 eV, a value in the range of the GZK bound [1, 2]. The nature of the primary particles causing these events is controversial. If the primaries are |
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