Simulation study of GZK photon fluxes

TL;DR

This paper uses Monte Carlo simulations to study the expected fluxes of GZK photons from ultra-high energy cosmic ray sources, analyzing various scenarios and their detectability with current and future experiments.

Contribution

It provides a detailed simulation-based analysis of GZK photon fluxes, considering different source and propagation scenarios, and assesses their observability in upcoming cosmic ray experiments.

Findings

Current limits constrain exotic photon production scenarios.

Expected GZK photon fluxes may be detectable with future experiments.

Source parameters of Centaurus A can be tested via GZK photon observations.

Abstract

The composition of ultra-high energy (UHE) cosmic rays E>10^17 eV is still unknown. The observation of UHE photons would extend the observed electromagnetic spectrum to highest energy and open a new channel for multimessenger observations in the universe. Current limits on the photon flux already constrain ``exotic'' scenarios where a large number of photons is expected by the decay products of supermassive X-particles. Motivated by the growing exposure of UHE cosmic ray experiments - like the Pierre Auger Observatory - the observation of conventionally produced GZK photons may be in reach in the near future. We investigate UHE particle propagation using the Monte Carlo code CRPropa. Particularly, the expected photon fluxes normalized to current experiments as well as prospects for future experiments are illustrated. Varying source and propagation scenarios are analyzed and the impact on secondary GZK photons is shown. For the specific case of Centaurus A, we study which source parameters can be tested by searching for the expected GZK photons.