The spectrum of about 6 × ${10}^5$ muons in the zenith angle range $\theta =68\mathrm{}°-82\mathrm{}°$ and the energy range $E=1-1000\mathrm{}$ GeV has been measured by a Kiel-Desy collaboration at Hamburg. The data are represented by a simple form fit which goes as $E^{-2.57\mathrm{}}$sec $\theta$ for the integral spectrum at very high energies. indicating that the galactic cosmic-ray nucleon spectrum is flatter than $E^{-2.75\mathrm{}}$ beyond 1000 GeV.

• Received 23 October 1978

DOI:https://doi.org/10.1103/PhysRevD.19.1368