Cosmic PeV Neutrinos and the Sources of Ultrahigh Energy Protons
  The IceCube experiment recently detected the first flux of high-energy
neutrinos in excess of atmospheric backgrounds. We examine whether these
neutrinos originate from within the same extragalactic sources as
ultrahigh-energy cosmic rays. Starting from rather general assumptions about
spectra and flavors, we find that producing a neutrino flux at the requisite
level through pion photoproduction leads to a flux of protons well below the
cosmic-ray data at ~10^18 eV, where the composition is light, unless
pions/muons cool before decaying. This suggests a dominant class of accelerator
that allows for cosmic rays to escape without significant neutrino yields.
