Propagation of Ultra-High Energy Nucleus in the Intergalactic Photon Field

We present a calculation of nuclei propagation with energyes above 1018 eV in the intergalactic photon field. The calculation is based on a Monte Carlo approach for the nucleus-photon interaction as well as intergalactic magnetic field. We assume that the Ultra-High Energy Cosmic Rays (UHECR) are nuclei which are emitted from extra-galactic point sources. Four bumps are found in the energy spectrum of UHECR which make clusters in the distribution of its arrival directions. Based on this calculation, the energy distribution of the cluster events is discussed.