Search for photons at the Pierre Auger Observatory

TL;DR

The paper discusses the Pierre Auger Observatory's efforts to detect ultra-high energy photons, highlighting its potential to test cosmic ray origins and fundamental physics, including Lorentz violation constraints.

Contribution

It presents the first experimental limits on ultra-high energy photons from the Observatory, demonstrating their importance in astrophysics and fundamental physics research.

Findings

Limits on ultra-high energy photon flux established

Constraints on Lorentz violation derived

Implications for cosmic ray origin theories

Abstract

The Pierre Auger Observatory has a unique potential to search for ultra-high energy photons (above ~1 EeV). First experimental limits on photons were obtained during construction of the southern part of the Observatory. Remarkably, already these limits have proven useful to falsify proposals about the origin of cosmic rays, and to perform fundamental physics by constraining Lorentz violation. A final discovery of photons at the upper end of the electromagnetic spectrum is likely to impact various branches of physics and astronomy.