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Cosmogenic neutrinos from the propagation of ultrahigh energy nuclei


We calculate the flux of neutrinos generated by the propagation of ultrahigh energy nuclei over cosmological distances. The propagation takes into account the interactions with cosmic background radiations including the CMB and the most recent estimates of higher energy (infrared, optical, and ultraviolet) backgrounds. We assume that the composition of ultrahigh energy cosmic rays (UHECRs) at the source is the same as the one observed at low energies. This assumption fits the present data well at the highest energies. We compare the cosmogenic neutrino flux from mixed composition sources to that from pure proton sources. We find that the neutrino flux in the mixed composition case has a high energy peak, mainly due to photopion production off CMB photons, of similar shape and amplitude to those in the proton case. At low energies both composition cases have significant neutrino flux with a peak around 10 14.5 eV due to the higher energy backgrounds. The mixed composition case induces a higher flux of neutrinos at energies below 1013 eV due to the neutron decay component that extends down to low energies. Detection of diffuse neutrino fluxes at ultrahigh energies can strongly constrain the source distribution of UHECRs whereas fluxes at lower energies could be used to constrain confinement of VHE and UHE cosmic rays if combined with composition analysis from cosmic ray experiments. © IOP Publishing Ltd.

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