Electromagnetic Dissociation at Cosmic-ray Energies

Electromagnetic dissociation (EMD) is a well-known process that has been extensively studied using accelerator beams. However, the influence of EMD on cosmic-ray propagation in the atmosphere and galaxy remains unclear. For instance, understanding the origin of ultra-high energy cosmic rays requires knowledge of their mass composition. This can be determined by measuring the depth of the maximum of air shower development (X₌₀ₗ) and, in particular, the fluctuations of showers around their mean. Due to its substantial cross section, EMD could modify these observables, especially for heavy nuclei. This paper presents reliable predictions of cross sections, particle yields, and nuclear fragments produced in electromagnetic dissociation interactions at cosmic-ray energies for various projectiles on air. A brief description of the model for predicting EMD cross sections and subsequent (virtual) photon interactions is provided. This model is embedded in the FLUKA code, has been validated, and has been used at energies ranging from a few GeV/n to LHC energies. Recently, the virtual and real photon interaction models in FLUKA have been significantly improved; a brief description of these changes is included. The impact of EMD interactions on cosmic-ray showers in the atmosphere is shown to be minimal. At the same time, FLUKA's sophisticated photo-nuclear models have also been applied to explore their suitability for extragalactic cosmic ray propagation studies. A preliminary calculation of the energy loss length, considering the cosmic microwave background (CMB) and extragalactic background light (EBL) radiation fields, is presented for several ions ranging from protons to uranium.