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The Pierre Auger Observatory is a facility built to detect air showers produced by cosmic rays above 10^17 eV. During clear nights with a low illuminated moon fraction, the UV fluorescence light produced by air showers is recorded by…
The energy spectrum of ultra-high energy cosmic rays (UHECRs) provides essential information on the most energetic phenomena in the Universe. Beyond EeV energies, the Telescope Array and Pierre Auger Observatory have the largest exposures…
Data taken at the Pierre Auger Observatory are used to search for air showers initiated by ultra-high energy (UHE) photons. Results of searches are reported from hybrid observations where events are measured with both fluorescence and array…
Ultra-high energy cosmic rays (UHECRs) are extremely energetic charged particles that originate from outer space. The Telescope Array (TA) experiment, the largest UHECR observatory in the Northern Hemisphere, has provided high-precision…
Recent measurements suggest that extensive air showers initiated by ultra-high energy cosmic rays (UHECR) emit signals in the microwave band of the electromagnetic spectrum caused by the collisions of the free-electrons with the atmospheric…
The High Elevation Auger Telescopes (HEAT) are three tiltable fluorescence telescopes which represent a low energy enhancement of the fluorescence telescope system of the southern site of the Pierre Auger Observatory in Argentina. The…
Calibrating the absolute energy scale of air showers initiated by ultra-high energy cosmic rays is an important experimental issue. Currently, the corresponding systematic uncertainty amounts to 14-21% using the fluorescence technique. Here…
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 interaction of Ultra High Energy Cosmic Rays (UHECRs) with the atoms of the atmosphere can occur at center-of-mass energies that surpass 100 TeV, while present human-made accelerators go up to 13 TeV. Therefore it provides a unique…
We present a concept for on-orbit radio detection of ultra-high energy cosmic rays (UHECRs) that has the potential to provide collection rates of ~100 events per year for energies above 10^20 eV. The synoptic wideband orbiting radio…
The detection of astrophysical neutrinos by IceCube in the TeV-PeV energy range motivates the development of instruments for observing these particles at higher energies. Moreover, the detection of very-high-energy (VHE) neutrinos could…
High-energy cosmic rays with energies exceeding $10^{17}$ eV are frequently observed by measurements of the fluorescence light induced by air showers. A major contribution to the systematic uncertainties of the absolute energy scale of such…
The Pierre Auger Observatory is the world's largest operating detection system for the observation of ultra high energy cosmic rays (UHECRs). The detector allows detailed measurements of their energy spectrum, mass composition and arrival…
The origin of ultra-high-energy cosmic rays (UHECRs) is one of the intriguing mysteries in astroparticle physics. In order to identify their sources, we need precise knowledge of the mass composition of UHECRs. The direct detection of…
The Yakutsk array observes the Cherenkov light emitted by UHECR in atmosphere. Recently, an autonomous subarray is added consisting of photomultipliers to measure the showers in the knee region. Our aim is to analyze the combined data set…
Ultra-high energy cosmic rays (UHECRs) have been studied with the data of the Pierre Auger Observatory for more than fifteen years. An essential feature of the Observatory is its hybrid design: UHECRs are detected through the observation of…
The World Space Observatory - Ultraviolet (WSO-UV) space telescope is equipped with high dispersion (55,000) spectrographs working in the 1150-3100 {\AA} spectral range. To evaluate the impact of the design on the scientific objectives of…
The Joint Experiment Missions for Extreme Universe Observatory comprises a collection of complementary missions dedicated to pioneering technologies and techniques for a future space-based multi-messenger observatory which will have…
The status of the field of ultrahigh energy cosmic rays is summarized, from the point of view of the latest results of the High Resolution Fly's Eye (HiRes) Experiment. HiRes results are presented, and compared with those of the Akeno Giant…
The Telescope Array (TA) is the largest ultra-high energy cosmic ray (UHECR) observatory in the Northern Hemisphere. Together with its extensions, TA Low Energy (TALE), TALE infill, and the TA$\times$4 array, it measures extensive air…