Search for Ultra-High Energy Photons with the Pierre Auger Observatory

TL;DR

This paper reviews the search for ultra-high energy photons using the Pierre Auger Observatory, highlighting the current limits on photon fluxes and implications for cosmic-ray and exotic particle models.

Contribution

It summarizes the current status and future prospects of ultra-high energy photon searches at the Pierre Auger Observatory, including constraints on theoretical models.

Findings

Stringent limits on ultra-high energy photon fluxes

Constraints on exotic particle decay models

Near detection sensitivity for cosmogenic photons

Abstract

One of key scientific objectives of the Pierre Auger Observatory is the search for ultra-high energy photons. Such photons could originate either in the interactions of energetic cosmic-ray nuclei with the cosmic microwave background (so-called cosmogenic photons) or in the exotic scenarios, e.g. those assuming a production and decay of some hypothetical super-massive particles. The latter category of models would imply relatively large fluxes of photons with ultra-high energies at Earth, while the former, involving interactions of cosmic-ray nuclei with the microwave background - just the contrary: very small fractions. The investigations on the data collected so far in the Pierre Auger Observatory led to placing very stringent limits to ultra-high energy photon fluxes: below the predictions of the most of the exotic models and nearing the predicted fluxes of the cosmogenic photons. In this paper the status of these investigations and perspectives for further studies are summarized.