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 similar to 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.