Abstract
Ultra high energy cosmic rays (UHECRs) are expected to be accelerated in astrophysical sources and to travel through extragalactic space before hitting the Earth atmosphere. They interact both with the environment in the source and with the intergalactic photon fields they encounter, causing different processes at various scales depending on the photon energy in the nucleus rest frame. UHECR interactions are sensitive to uncertainties in the extragalactic background spectrum and in the photo-disintegration models.
Highlights
Ultra high energy cosmic rays (UHECRs) are expected to be accelerated in astrophysical sources and to travel through extragalactic space before hitting the Earth atmosphere
This assumption can be tested in light of the UHECR energy spectrum measurements from the TA collaboration [3] and the upper bound on the flux of cosmogenic neutrinos from the IceCube collaboration [16], as done in [15]
The presence of protons in UHECRs can be constrained by considering the photons that are produced during propagation, in the light of the recent results obtained by the Fermi-LAT collaboration about the origin of the EBL [18]
Summary
The ankle, i.e. the hardening at about 5 × 1018 eV, in the proton dip model, is expected to be due to energy losses due to electronpositron pair production mainly on CMB [9]. The astrophysical scenario is complicated by the fact that source properties, as for example their distribution and their acceleration power, are unknown: the suppression of the flux, even in the pure-proton composition case, cannot be addressed to GZK cutoff in absence of knowledge about sources [12]. Since the threshold energy for photo-meson production (roughly) increases ∝ A, the suppression of the flux in case of a mixed composition is expected to be due, at least partly, to the photo-disintegration of nuclei, occurring after the excitation of the giant dipole resonance (GDR, ≈8 MeV in the NRF) that follows the absorption of a CMB or EBL photon [13, 14]. From the point of view of the models, a self-consistent interpretation of the spectrum and composition results of the Auger Observatory and the Telescope Array experiment can be used to limit the astrophysical scenarios compatible with data
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
