Evidence for a High-Energy Cosmic-Ray Spectrum Cutoff

R. M. Baltrusaitis; R. Cady; G. L. Cassiday; R. Cooper; J. W. Elbert; P. R. Gerhardy; S. Ko; E. C. Loh; Y. Mizumoto; M. Salamon; P. Sokolsky; D. Steck

doi:10.1103/PhysRevLett.54.1875

Evidence for a High-Energy Cosmic-Ray Spectrum Cutoff

R. M. Baltrusaitis, R. Cady, G. L. Cassiday, R. Cooper, J. W. Elbert, P. R. Gerhardy, S. Ko, E. C. Loh, Y. Mizumoto, M. Salamon, P. Sokolsky, and D. Steck

Phys. Rev. Lett. 54, 1875 – Published 22 April 1985

Abstract

We report a measurement of the ultrahigh-energy cosmic-ray spectrum using an atmospheric fluorescence technique for extensive-air-shower detection. The differential spectrum between 0.1 and 10 EeV (1 EeV = $10^{18}$ eV) is well fitted by a power law with slope 2.94±0.02. Above 10 EeV evidence is presented for the development of a spectral "bump" followed by a cutoff at 70 EeV.

Received 11 February 1985

DOI:https://doi.org/10.1103/PhysRevLett.54.1875

Authors & Affiliations

R. M. Baltrusaitis, R. Cady^*, G. L. Cassiday, R. Cooper, J. W. Elbert, P. R. Gerhardy, S. Ko, E. C. Loh, Y. Mizumoto, M. Salamon^†, P. Sokolsky, and D. Steck

Department of Physics, University of Utah, Salt Lake City, Utah 84112

^*Present address: Department of Physics, University of Hawaii, Honolulu, Haw. 96822.
^†Present address: Department of Physics, University of California, Berkeley, Cal. 94720.