Related papers: Improving photon-hadron discrimination based on co…

A search for ultra-high energy photons with energies above 1 EeV is performed using nine years of data collected by the Pierre Auger Observatory in hybrid operation mode. An unprecedented separation power between photon and hadron primaries…

The identification of very high energy photons is of great importance for the understanding of the origin of extreme energy cosmic rays (EECR). Several can be the sources of high energy photons at Earth. A guaranteed component is the flux…

The origin of the highest energy cosmic rays is still unknown. At present, the major uncertainties are located at energies above $\sim 10^{19.5}$ eV, the expected beginning of the GZK suppression. This is mainly due to the low statistics…

The Pierre Auger Observatory is the most sensitive instrument to detect photons with energies above $10^{17}$ eV. It measures extensive air showers generated by ultra high energy cosmic rays using a hybrid technique that exploits the…

A method is developed to search for air showers initiated by photons using data recorded by the surface detector of the Auger Observatory. The approach is based on observables sensitive to the longitudinal shower development, the signal…

Measurements of air showers made using the hybrid technique developed with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for point sources of EeV photons anywhere in the exposed sky. A…

Ultra-high-energy photons have long been sought as tracers of the most energetic processes in the Universe. Several sources can contribute to a diffuse photon flux, including interactions of cosmic rays with Galactic matter and radiation…

We describe a method to analyse inclined air showers produced by ultra high energy cosmic rays using an analytical description of the muon densities. We report the results obtained using data from inclined events…

A photon induced shower at $E_{prim}\ge 10^{18}$ eV exhibits very specific features and is different from a hadronic one. At such energies, the LPM effect delays in average the first interactions of the photon in the atmosphere and hence…

Ultra-high-energy photons play an important role in probing astrophysical models and beyond-Standard-Model scenarios. We report updated limits on the diffuse photon flux using Telescope Array's Surface Detector data collected over 14 years…

We present a new method to derive an upper limit on the ultra-high-energy (UHE) photon flux above a given energy, using the Auger SD events. As previous studies, it takes advantage of the fundamental differences between showers induced by…

Experimental conclusions from air shower observations on cosmic-ray photons above 10^19 eV are based on the comparison to detailed shower simulations. For the calculations, the photonuclear cross-section needs to be extrapolated over…

We present the results of the search for ultra-high-energy photons with nine years of data from the Telescope Array surface detector. A multivariate classifier is built upon 16 reconstructed parameters of the extensive air shower. These…

Comparing the signals measured by the surface and underground scintillator detectors of the Yakutsk Extensive Air Shower Array, we place upper limits on the integral flux and the fraction of primary cosmic-ray photons with energies E >…

The surface detector (SD) of the Telescope Array (TA) experiment allows one to indirectly detect photons with energies of order $10^{18}$ eV and higher and to separate photons from the cosmic-ray background. In this paper we present the…

A major challenge in ground-based ultra-high-energy gamma-ray observations remains in discriminating sporadic gamma-ray signals from a huge background of cosmic-ray events. To achieve good discrimination power of gamma rays against protons,…

Several gamma-ray observatories have discovered photons of cosmic origin with energies in the PeV ($10^{15}\,\text{eV}$) range. Photons at these energies might be produced as by-products from particle acceleration in so-called PeVatrons,…

The current methods to determine the primary energy of ultra-high energy cosmic rays (UHECRs) are different when dealing with hadron or photon primaries. The current experiments combine two different techniques, an array of surface…

From direct observations of the longitudinal development of ultra-high energy air showers performed with the Pierre Auger Observatory, upper limits of 3.8%, 2.4%, 3.5% and 11.7% (at 95% c.l.) are obtained on the fraction of cosmic-ray…

We use the surface detector of the Pierre Auger Observatory to search for air showers initiated by photons with an energy above $10^{19}$ eV. Photons in the zenith angle range from 30$^\circ$ to 60$^\circ$ can be identified in the…