Investigation on mass composition of UHE cosmic rays using CRPropa 2.0
  In this paper, we used the Monte Carlo code CRPropa version 2.0 to simulate the propagation of UHE cosmic rays. In the simulation, uniform cosmic ray sources with spectral indices of {\alpha} = 1.4, {\alpha} = 2 and Emax = 1021 eV for pure iron composition at the source position are assumed. We obtained the logarithmic average mass of cosmic rays as a function of energy and compared it with the experimental values in the ankle, and we demonstrated how the mass composition changes before and after the ankle. 
Gohar Rastegarzade and Bahare Parvizi
astro-ph.HE