Constraining Dark Matter and Ultra-High Energy Cosmic Ray Sources with Fermi-LAT Diffuse Gamma Ray Background

TL;DR

This paper uses Fermi-LAT gamma-ray background data to constrain models of ultra-high energy cosmic rays and decaying dark matter, providing limits on particle decay times and cosmic ray origins.

Contribution

It introduces a novel approach combining gamma-ray background measurements with cosmic ray and dark matter models to set new constraints.

Findings

Constraints on UHECR source models from gamma-ray data

Limits on dark matter decay times based on gamma-ray background

Minimal gamma-ray flux estimates from UHECR interactions

Abstract

We use the recent measurement of the isotropic $\gamma$-ray background (IGRB) by Fermi LAT and analysis of the contribution of unresolved point $\gamma$-ray sources to IGRB to build constraints on the models of ultra-high cosmic rays (UHECR) origin. We also calculate the minimal expected diffuse $\gamma$-ray flux produced by UHECR interactions with an interstellar photon background. Finally, for the subclass of dark matter (DM) models with decaying weakly interacting massive particles (WIMP), we build constraints on the particle decay time using minimal expected contributions to the IGRB from unresolved point $\gamma$-ray sources and UHECR.