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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…

High Energy Astrophysical Phenomena · Physics 2025-10-06 Jihyun Kim , Dmitri Ivanov , Gordon Thomson

Previous measurements of the composition of Ultra-High Energy Cosmic Rays(UHECRs) made by the High Resolution Fly's Eye(HiRes) and Pierre Auger Observatory(PAO) are seemingly contradictory, but utilize different detection methods, as HiRes…

High Energy Astrophysical Phenomena · Physics 2015-06-22 R. U. Abbasi , M. Abe , T. Abu-Zayyad , M. Allen , R. Anderson , R. Azuma , E. Barcikowski , J. W. Belz , D. R. Bergman , S. A. Blake , R. Cady , M. J. Chae , B. G. Cheon , J. Chiba , M. Chikawa , W. R. Cho , T. Fujii , M. Fukushima , T. Goto , W. Hanlon , Y. Hayashi , N. Hayashida , K. Hibino , K. Honda , D. Ikeda , N. Inoue , T. Ishii , R. Ishimori , H. Ito , D. Ivanov , C. C. H. Jui , K. Kadota , F. Kakimoto , O. Kalashev , K. Kasahara , H. Kawai , S. Kawakami , S. Kawana , K. Kawata , E. Kido , H. B. Kim , J. H. Kim , J. H. Kim , S. Kitamura , Y. Kitamura , V. Kuzmin , Y. J. Kwon , J. Lan , S. I. Lim , J. P. Lundquist , K. Machida , K. Martens , T. Matsuda , T. Matsuyama , J. N. Matthews , M. Minamino , Y. Mukai , I. Myers , K. Nagasawa , S. Nagataki , T. Nakamura , T. Nonaka , A. Nozato , S. Ogio , J. Ogura , M. Ohnishi , H. Ohoka , K. Oki , T. Okuda , M. Ono , A. Oshima , S. Ozawa , I. H. Park , M. S. Pshirkov , D. C. Rodriguez , G. Rubtsov , D. Ryu , H. Sagawa , N. Sakurai , A. L. Sampson , L. M. Scott , P. D. Shah , F. Shibata , T. Shibata , H. Shimodaira , B. K. Shin , H. S. Shin , J. D. Smith , P. Sokolsky , R. W. Springer , B. T. Stokes , S. R. Stratton , T. Stroman , T. Suzawa , M. Takamura , M. Takeda , R. Takeishi , A. Taketa , M. Takita , Y. Tameda , H. Tanaka , K. Tanaka , M. Tanaka , S. B. Thomas , G. B. Thomson , P. Tinyakov , I. Tkachev , H. Tokuno , T. Tomida , S. Troitsky , Y. Tsunesada , K. Tsutsumi , Y. Uchihori , S. Udo , F. Urban , G. Vasiloff , T. Wong , R. Yamane , H. Yamaoka , K. Yamazaki , J. Yang , K. Yashiro , Y. Yoneda , S. Yoshida , H. Yoshiia , R. Zollinger , Z. Zundel

The clustering of ultra high energy (above 5\cdot 10^{19} eV) cosmic rays (UHECR) suggests that they might be emitted by compact sources. We present a statistical analysis on the source density based on the multiplicities. The propagation…

High Energy Physics - Phenomenology · Physics 2015-06-25 Z. Fodor

Using the Auger mass-composition analysis of ultra high energy cosmic rays, based on the shape-fitting of $X_{max}$ distributions, we demonstrate that mass composition and energy spectra measured by Auger, Telescope Array and HiRes can be…

High Energy Astrophysical Phenomena · Physics 2019-04-11 R. Aloisio , V. Berezinsky

We introduce a novel method for identifying the mass composition of ultra-high-energy cosmic rays using deep learning. The key idea of the method is to use a chain of two neural networks. The first network predicts the type of a primary…

Instrumentation and Methods for Astrophysics · Physics 2022-05-18 O. Kalashev , I. Kharuk , M. Kuznetsov , G. Rubtsov , T. Sako , Y. Tsunesada , Ya. Zhezher

Ultra-high-energy cosmic rays (UHECRs) are atomic nuclei from space with vastly higher energies than any other particles ever observed. Their origin and chemical composition remain a mystery. As we show here, the large- and…

High Energy Astrophysical Phenomena · Physics 2021-06-02 Chen Ding , Noemie Globus , Glennys R. Farrar

The determination of the mass composition of the highest energy cosmic rays is one of the greatest challenges in cosmic ray experiments. The highest energy cosmic rays are only detected indirectly because of their very low flux. Using the…

High Energy Astrophysical Phenomena · Physics 2019-08-13 J. A. Bellido

The shape of the longitudinal development of the showers generated in the atmosphere by very high energy cosmic ray particles encodes information about the mass composition of the flux, and about the properties of hadronic interactions that…

High Energy Astrophysical Phenomena · Physics 2021-05-19 Paolo Lipari

The Pierre Auger Observatory has driven the field of ultra-high-energy cosmic ray (UHECR) physics, producing several groundbreaking observations over the last 20 years. One of the most striking findings has been the complex evolution of…

High Energy Astrophysical Phenomena · Physics 2025-07-22 Eric Mayotte

The clustering of ultra high energy (above 10^20 eV) cosmic rays (UHECR) suggests that they might be emitted by compact sources. Statistical analysis of Dubovsky et al. (Phys. Rev. Lett. 85 (2000) 1154) estimated the source density. We…

High Energy Physics - Phenomenology · Physics 2009-12-31 Z. Fodor , S. D. Katz

The nature of ultrahigh-energy cosmic rays (UHECRs) at energies >10^20 eV remains a mystery. They are likely to be of extragalactic origin, but should be absorbed within ~50 Mpc through interactions with the cosmic microwave background. As…

Astrophysics · Physics 2009-11-11 H. Falcke , W. D. Apel , A. F. Badea

Detection of (ultra-) high-energy cosmic rays with the use of radio frequency emission from extensive air showers has been proven as complimentary to existing ground array detection techniques. Great progress has been made in the…

Instrumentation and Methods for Astrophysics · Physics 2019-08-13 Sijbrand de Jong

Ground based observations appear to indicate that Ultra High Energy Cosmic Rays (UHECR) of the highest energies (>10^{18.7} eV) consist of heavy particles -- shower depth and muon production data both pointing towards this conclusion. On…

High Energy Astrophysical Phenomena · Physics 2025-09-18 S. Romanopoulos , V. Pavlidou , T. Tomaras

The latest observations of extensive air showers (EAS) induced by ultra-high-energy cosmic rays (UHECR) appear to indicate, prima facie, a transition to heavy primaries at the highest energies. However, this interpretation, which is based…

High Energy Astrophysical Phenomena · Physics 2019-06-26 Vasiliki Pavlidou , Theodore Tomaras

Large-scale accretion shocks around massive clusters of galaxies, generically expected in the cold dark matter scenario of cosmological structure formation, are shown to be plausible sources of the observed ultrahigh energy cosmic rays…

Astrophysics · Physics 2008-03-10 Susumu Inoue , Guenter Sigl , Francesco Miniati , Eric Armengaud

The composition of Ultra High Energy Cosmic Rays (UHECR) is measured with the High Resolution Fly's Eye cosmic ray observatory (HiRes) data using the Xmax technique. Data were collected in stereo between 1999 November and 2001 September.…

Astrophysics · Physics 2008-11-26 s Eye Collaboration

Ultra-High-Energy Cosmic Rays (UHECRs), particles characterized by energies exceeding $10^{18}$ eV, are generally believed to be accelerated electromagnetically in high-energy astrophysical sources. One promising mechanism of UHECR…

High Energy Astrophysical Phenomena · Physics 2024-12-10 Luca Comisso , Glennys R. Farrar , Marco S. Muzio

The results from the first three years observation in Telescope Array are reviewed. The energy spectrum, mass composition, and anisotropy in arrival directions of ultra-high energy cosmic rays are discussed. The energy spectrum of cosmic…

High Energy Astrophysical Phenomena · Physics 2019-08-13 Yoshiki Tsunesada

We present an updated cosmic-ray mass composition analysis in the energy range $10^{16.8}$ to $10^{18.3}$ eV from 334 air showers measured with the LOFAR radio telescope, and selected for minimal bias. In this energy range, the origin of…

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…

High Energy Astrophysical Phenomena · Physics 2015-04-17 G. Ros , G. A. Medina-Tanco , A. D. Supanitsky , L. del Peral , M. D. Rodríguez-Frías