Neutrinos as a signature of ultrahigh energy photons at high redshift

Sources of ultrahigh energy photons operating at high redshift produce a diffuse background of neutrinos. At high redshift, when the cosmic microwave background radiation has a higher temperature, an electromagnetic cascade originated by an energetic photon can generate neutrinos via muon and pion production and decay. We calculate numerically the neutrino spectrum of the cascade neutrinos produced by various photon sources (which need not necessarily generate a large flux of primary neutrinos). A distinctive feature of this flux is a ''bump'' in the neutrino spectrum at energies E∼1017 eV. The detection of such neutrinos can help us understand the origin of ultrahigh energy cosmic rays