A Search for Photons with Energies Above 2 × 10¹⁷ eV Using Hybrid Data from the Low-Energy Extensions of the Pierre Auger Observatory

Abstract

Ultra-high-energy photons with energies exceeding 1017 eV offer a wealth of connections to different aspects of cosmic-ray astrophysics as well as to gamma-ray and neutrino astronomy. The recent observations of photons with energies in the 1015 eV range further motivate searches for even higher-energy photons. In this paper, we present a search for photons with energies exceeding 2 × 1017 eV using about 5.5 yr of hybrid data from the low-energy extensions of the Pierre Auger Observatory. The upper limits on the integral photon flux derived here are the most stringent ones to date in the energy region between 1017 and 1018 eV.

Cosmological implications of photon-flux upper limits at ultrahigh energies in scenarios of Planckian-interacting massive particles for dark matter

“…Three different analyses, differing in the detector used, have been developed to cover the wide energy range probed at the Observatory and have been reported in Refs. [62][63][64]. No photons with energies above 2 × 10 8 GeV have been unambiguously identified so far, leading to the 95% CL flux upper limits displayed in Fig.…”

Searches for ultra-high energy photons and neutrinos with the Pierre Auger Observatory

“…The upper limits on the integral UHE photon flux established by Auger (circles) [8]. Shown also are previous results by various experiments in triangles and squares: KASCADE-Grande [30], EAS-MSU [31] and Telescope Array [32].…”

“…The hybrid data acquired by the low-energy extensions of the SD and FD are explored to discriminate a photon signal among the hadronic background above 2 × 10 17 eV [8]. For this task, the direct measurements of max are complemented by the observable =4 defined as = × 1000 m that combines the measured signals recorded by stations located at a distance from the shower axis.…”

Search for Ultra-high-energy Photons from Gravitational Wave Sources with the Pierre Auger Observatory

“…With its different detector components and various enhancements, the observatory is also sensitive to a possible component of primary photons. Different searches have been performed aiming to identify such a component among the diffuse flux of cosmic rays (Aab et al 2017a;Abreu et al 2023Abreu et al , 2022, as well as from steady point sources in the sky (Aab et al 2017b). No statistically significant excess of primary UHE photons has been identified so far, and the strongest constraints to date on the flux of photons from 2 × 10 17 eV up to energies beyond 10 20 eV have been obtained.…”