Search for primary photons at tens of PeV with the Pierre Auger Observatory

Collaboration
Jul 25, 2023
13 pages
Published in:
  • PoS ICRC2023 (2023) 238
Contribution to:
  • Published: Jul 25, 2023
Experiments:

Citations per year

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Abstract: (SISSA)
The observation of primary photons with energies around 101610^{16} eV would be particularly interesting after the discovery of Galactic gamma-ray sources with spectra extending into the PeV range. Since photons are connected to the acceleration of charged particles, searches for photons enhance the multi-messenger understanding of cosmic-ray sources as well as of transient astrophysical phenomena, while offering wealthy connections to neutrino astronomy and dark matter. Additionally, diffuse photon fluxes are expected from cosmic-ray interactions with Galactic matter and background radiation fields. Previously, the energy domain between 11 and 200200 PeV was only explored from the Northern Hemisphere. The Pierre Auger Observatory is the largest astroparticle experiment in operation and, thanks to its location, has a sizable exposure to the Southern sky, including the Galactic center region. In this contribution, we present the first search for photons from the Southern hemisphere between 5050 and 200200 PeV exploiting the Auger data acquired during 4\sim4 yr of operation. We describe the method to discriminate photons against the dominating hadronic background; it is based on the measurements of air showers taken with the low-energy extension of the Pierre Auger Observatory composed by 1919 water-Cherenkov detectors spanning 2\sim2 km2^2 and an Underground Muon Detector. The search for a diffuse flux of photons is presented and its results are interpreted according to theoretical model predictions. This study extends the range of Auger photon searches to almost four decades in energy.
  • photon: primary
  • gamma ray: galaxy
  • radiation: background
  • background: hadronic
  • photon: flux
  • showers: atmosphere
  • charged particle: acceleration
  • muon: detector
  • cosmic radiation: interaction
  • Auger