Implications of the ultrahigh-energy cosmic-ray spectrum observed by the Fly’s Eye detector

We discuss the potential implications of the recent results of the Fly’s Eye detector on the ultrahigh-energy cosmic-ray spectrum. The data suggest that the observed slope flattening immediately prior to the cutoff appears to be a recoil-proton pileup associated with an $E^{\mathrm{-}2.5\pm .3}$ injection spectrum. We discuss the induced neutrino spectrum and its detectability in Fly’s Eye and DUMAND detectors.