The Effective Penetration Distance of Ultrahigh Energy Photons in the Cosmic Background Radiation and the Corresponding Neutrinos Production

We investigate the effective penetration lengths of UHE photons and related neutrinos production in the intergalactic space. Following the analytic method raised by Gould and Rephaeli (1978), the electromagnetic cascade initiated by a UHE photon would be studied, with paying particular attention to the leading particle in the cascade process. We obtain the effective penetration length of the leading particle by regarding the least energetic outgoing particles in the interaction processes as energy loss, as well as energy loss rate including the neutrino emission rate in the cascade process. Finally, we find that an extra component of UHE neutrinos will arise from the propagation of UHE cosmic rays due to the generated UHE photons and electron/positrons, with a flux reaching up to 10% of that of the conventional cosmogenic neutrino at a few EeV, in the absence of a strong intergalactic magnetic field and a strong cosmic radio background.CPCI-S(ISTP)179