Probing the Extragalactic Cosmic Rays origin with gamma-ray and neutrino backgrounds

TL;DR

This paper investigates the origins of extragalactic ultra-high-energy cosmic rays by analyzing gamma-ray and neutrino backgrounds, using recent Fermi-LAT and IceCube data to constrain source models and cosmological evolution.

Contribution

It provides a comprehensive analysis linking gamma-ray and neutrino observations to UHECR source characteristics, supporting a mixed-composition scenario consistent with multiple datasets.

Findings

Mixed-composition UHECR scenario aligns with Fermi-LAT and IceCube data.

Constraints on UHECR source evolution derived from gamma-ray and neutrino fluxes.

Cosmogenic gamma-ray and neutrino flux calculations support the mixed-composition model.

Abstract

GeV-TeV gamma-ray and PeV-EeV neutrino backgrounds provide a unique window on the nature of the ultra-high-energy cosmic-rays (UHECRs). We discuss the implications of the recent Fermi-LAT data regarding the extragalactic gamma-ray background (EGB) and related estimates of the contribution of point sources as well as IceCube neutrino data on the origin of the UHECRs. We calculate the diffuse flux of cosmogenic $\gamma$-rays and neutrinos produced during the UHECRs propagation and derive constraints on the possible cosmological evolution of UHECR sources. In particular, we show that the mixed-composition scenario which is in agreement with both (i) Auger measurements of the energy spectrum and composition up to the highest energies and (ii) the ankle-like feature in the light component detected by KASCADE-Grande, is compatible with both the Fermi-LAT measurements and with current IceCube limits.