Double pair production by ultra-high-energy cosmic ray photons

Using the CompHEP package, we provide a detailed estimate of the influence of double e ⁺ e ⁻ pair production (DPP) by photons on the propagation of ultra-high-energy electromagnetic cascades. We show that in the models where the cosmic ray photon energy reaches a few 10³ EeV, a refined DPP analysis may lead to a substantial difference in the predicted photon spectrum compared to the previous rough estimates. The article is published in the original.