Search for excess cosmic-ray events from the galactic plane

Abstract

Wdowczyk and Wolfendale1 have recently suggested that the cosmic-ray beam at 1015–1016 eV may contain a significant flux of γ rays from the direction of the galactic plane, and that this flux may affect the measured all-particle anisotropy and energy spectrum at these energies. We have searched for an excess of cosmic-ray events from the direction of the galactic plane. We can set upper limits which are close to the flux predicted by Wdowczyk and Wolfendale for the full galactic plane, and also for regions around the galactic centre. We have used these upper limits to place limits on the apparent brightness distribution of galactic γ-ray sources above 1015 eV, and on any contribution these sources can make to the cosmic-ray energy spectrum at the highest energies.

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Clay, R., Protheroe, R. & Gerhardy, P. Search for excess cosmic-ray events from the galactic plane. Nature 309, 687–688 (1984). https://doi.org/10.1038/309687a0

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