Abstract
With the newest version of our Monte Carlo code for ultra-high-energy cosmic ray (UHECR) propagation, CRPropa 3, the flux of neutrinos and photons due to interactions of UHECRs with extragalactic background light can be predicted. Together with the recently updated data for the isotropic diffuse gamma-ray background (IGRB) by Fermi LAT, it is now possible to severely constrain UHECR source models. The evolution of the UHECR sources especially plays an important role in the determination of the expected secondary photon spectrum. Pure proton UHECR models are already strongly constrained, primarily by the highest energy bins of Fermi LAT's IGRB, as long as their number density is not strongly peaked at recent times.
Highlights
The Fermi-LAT collaboration updated their measurements on the isotropic diffuse gammaray background (IGRB) and extended it up to 820 GeV [1]
A possible source for part of the IGRB is secondary electromagnetic cascades initiated by interactions of ultra-high-energy cosmic rays (UHECRs) with the cosmic microwave background (CMB) or the extragalactic background light (EBL)
The UHECR energy spectrum has been measured with unprecedented statistics by the Pierre Auger [3, 4] (Auger) and Telescope Array [5] (TA) collaborations
Summary
The Fermi-LAT collaboration updated their measurements on the isotropic diffuse gammaray background (IGRB) and extended it up to 820 GeV [1]. A possible source for part of the IGRB is secondary electromagnetic cascades initiated by interactions of ultra-high-energy cosmic rays (UHECRs) with the cosmic microwave background (CMB) or the extragalactic background light (EBL). In these same interactions secondary neutrinos can be produced. While the measurements of Auger show a depth of the shower maximum, Xmax, indicating an increasingly heavier mass composition for E 1018.3 eV [6], TA results in the same energy range are consistent with a pure proton composition [7]. DINT solves the one-dimensional transport equations for electromagnetic cascades initiated by electrons, positrons or photons and includes single, double and triplet pair production, inverseCompton scattering and synchrotron radiation
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