The intergalactic propagation of ultra-high energy cosmic ray nuclei
  We investigate the propagation of ultra-high energy cosmic ray nuclei (A = 1-56) from cosmologically distant sources through the cosmic radiation backgrounds. Various models for the injected composition and spectrum and of the cosmic infra-red background are studied using updated photo-disintegration cross-sections. The observational data on the spectrum and the composition of ultra-high energy cosmic rays are jointly consistent with a model where all of the injected primary cosmic rays are iron nuclei (or a mixture of heavy and light nuclei). 
Dan Hooper (Fermilab), Subir Sarkar (Oxford) and Andrew M. Taylor   (Oxford)