Upper Limit on the Photon Fraction in Highest-Energy Cosmic Rays from AGASA Data

Journal Article · Fri Oct 21 04:00:00 EDT 2005 · Physical Review Letters

DOI:https://doi.org/10.1103/PhysRevLett.95.171102· OSTI ID:20699460

Risse, M ^[1]; Homola, P; Gora, D; Pekala, J; Wilczynska, B; Wilczynski, H ^[1]; Engel, R; Heck, D ^[2]

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1. Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Cracow (Poland)
2. Forschungszentrum Karlsruhe, Institut fuer Kernphysik, 76021 Karlsruhe (Germany)

A new method to derive an upper limit on photon primaries from small data sets of air showers is developed which accounts for shower properties varying with the primary energy and arrival direction. Applying this method to the highest-energy showers recorded by the AGASA experiment, an upper limit on the photon fraction of 51% (67%) at a confidence level of 90% (95%) for primary energies above 1.25x10{sup 20} eV is set. This new limit on the photon fraction above the Greisen-Zatsepin-Kuzmin cutoff energy constrains the Z-burst model of the origin of highest-energy cosmic rays.

• OSTI ID: 20699460
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 17 Vol. 95; ISSN 0031-9007; ISSN PRLTAO
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC SHOWERS
EEV RANGE
ENERGY SPECTRA
PHOTONS
PRIMARY COSMIC RADIATION