Comparison of the ultrahigh energy cosmic ray flux observed by AGASA, HiRes, and Auger

Journal Article · Tue Aug 15 04:00:00 EDT 2006 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.74.043001· OSTI ID:20870938

Connolly, B M; BenZvi, S Y; Finley, C B; O'Neill, A C; Westerhoff, S ^[1]

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1. Department of Physics, Columbia University and Nevis Laboratories, New York, New York 10027 (United States)

The current measurements of the cosmic ray energy spectrum at ultra-high energies (E>10{sup 19} eV) are characterized by large systematic errors and poor statistics. In addition, the experimental results of the two experiments with the largest published data sets, AGASA and HiRes, appear to be inconsistent with each other, with AGASA seeing an unabated continuation of the energy spectrum even at energies beyond the Greisen-Zatsepin-Kuzmin cutoff energy at 10{sup 19.6} eV. Given the importance of the related astrophysical questions regarding the unknown origin of these highly energetic particles, it is crucial that the extent to which these measurements disagree be well understood. Here we evaluate the consistency of the two measurements for the first time with a model-independent method that accounts for the large statistical and systematic errors of current measurements. We further compare the AGASA and HiRes spectra with the recently presented Auger spectrum. The method directly compares two measurements, bypassing the introduction of theoretical models for the shape of the energy spectrum. The inconsistency between the observations is expressed in terms of a Bayes factor, a standard statistic defined as the ratio of a separate parent source hypothesis to a single parent source hypothesis. Application to the data shows that the two-parent hypothesis is disfavored. We expand the method to allow comparisons between an experimental flux and that predicted by any model.

• OSTI ID: 20870938
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 4 Vol. 74; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
AUGER ELECTRON SPECTROSCOPY
COMPARATIVE EVALUATIONS
COSMIC RAY DETECTION
COSMIC RAY FLUX
ENERGY SPECTRA
ERRORS
PEV RANGE
PRIMARY COSMIC RADIATION
STATISTICS