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A search for ultra-high-energy photons at the Pierre Auger Observatory exploiting air-shower universalityP. Savina,
Andrej Filipčič,
Jon Paul Lundquist,
Samo Stanič,
Serguei Vorobiov,
Danilo Zavrtanik,
Marko Zavrtanik,
Lukas Zehrer, 2022, published scientific conference contribution
Abstract: The Pierre Auger Observatory is the most sensitive detector to primary photons with energies
above ∼ 0.2 EeV. It measures extensive air showers using a hybrid technique that combines a
fluorescence detector (FD) with a ground array of particle detectors (SD). The signatures of a photon-induced air shower are a larger atmospheric depth at the shower maximum (Xmax) and a
steeper lateral distribution function, along with a lower number of muons with respect to the bulk of hadron-induced background. Using observables measured by the FD and SD, three photon
searches in different energy bands are performed. In particular, between threshold energies of 1–10 EeV, a new analysis technique has been developed by combining the FD-based measurement of Xmax with the SD signal through a parameter related to its muon content, derived from the universality of the air showers. This technique has led to a better photon/hadron separation and, consequently, to a higher search sensitivity, resulting in a tighter upper limit than before. The outcome of this new analysis is presented here, along with previous results in the energy ranges below 1 EeV and above 10 EeV. From the data collected by the Pierre Auger Observatory in about 15 years of operation, the most stringent constraints on the fraction of photons in the cosmic flux are set over almost three decades in energy.
Keywords: Pierre Auger Observatory, indirect detection, fluorescence detection, surface array, hybrid detection, ultra-high energy, cosmic rays, photons
Published in RUNG: 29.09.2023; Views: 733; Downloads: 5
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