Indications of proton-dominated cosmic-ray composition above 1.6 EeV.

  title={Indications of proton-dominated cosmic-ray composition above 1.6 EeV.},
  author={R. U. Abbasi and T. Abu-Zayyad and Mohammed A. Al-Seady and Monica Allen and J. F. Amman and R. Anderson and G. Archbold and Konstantin V. Belov and J. W. Belz and D. R. Bergman and Stephen Blake and O. A. Brusova and G. W. Burt and C. Cannon and Zhen Cao and W. Deng and Yulia Fedorova and Chad Finley and Richard Carl Gray and W. Hanlon and Cyrus M. Hoffman and M. H. Holzscheiter and D. Ivanov and Gareth Hughes and P. H{\"u}ntemeyer and B. F. Jones and Charles C. H. Jui and K. Kim and Malina Kirn and Eugene C. Loh and J. Liu and J. P. Lundquist and M. M. Maestas and Naohiro Manago and L. J. Marek and Kalen Martens and J. A. Matthews and J. N. Matthews and S. A. Moore and A. C. O'Neill and C. A. Painter and Lalith Padmasiri Perera and Kevin Alexander Reil and Robert Riehle and Michael D. Roberts and Diego Rodriguez and Naruo Sasaki and Steve Schnetzer and Lauren M. Scott and G. Sinnis and J. D. Smith and P. Sokolsky and C. Song and R. W. Springer and Bradford T. Stokes and Sean R. Stratton and S. B. Thomas and J. R. Jr. Thomas and Gordon Bennett Thomson and Dale Tupa and Andreas Zech and X. Z. Zhang},
  journal={Physical review letters},
  volume={104 16},
We report studies of ultrahigh-energy cosmic-ray composition via analysis of depth of air shower maximum (X(max)), for air shower events collected by the High-Resolution Fly's Eye (HiRes) observatory. The HiRes data are consistent with a constant elongation rate d/d[log(E)] of 47.9+/-6.0(stat)+/-3.2(syst) g/cm2/decade for energies between 1.6 and 63 EeV, and are consistent with a predominantly protonic composition of cosmic rays when interpreted via the QGSJET01 and QGSJET-II high-energy… 

Figures from this paper

Mass composition studies of Ultra High Energy cosmic rays through the measurement of the Muon Production Depths at the Pierre Auger Observatory
The Pierre Auger Observatory (Auger) in Argentina studies Ultra High Energy Cosmic Rays (UHECRs) physics. The flux of cosmic rays at these energies (above 1018 eV) is very low (less than 100
Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory
The Pierre Auger Collaboration has reported evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies E > Eth = 5.5 × 1019 eV. These show a correlation with
The spectra of BL Lac objects and Fanaroff–Riley I radio galaxies are commonly explained by the one-zone leptonic synchrotron self-Compton (SSC) model. Spectral modeling of correlated multiwavelength
The Fermi Large Area Telescope collaboration has recently reported on 50 months of measurements of the isotropic extragalactic gamma-ray background (EGRB) spectrum between 100 MeV and 820 GeV.


Forschungszentrum Karlsruhe
The transfer process of mechanical energy into electromagnetic energy is called the dynamo effect, which is believed to be the origin of the magnetic fields of many astrophysical bodies. First some
Mathematics of Statistics
THIS is the first volume of a second edition of a book first published in 1939. The complete book is intended to be an introduction to the more elementary theory and methods of mathematical
  • Phys. B, Proc. Suppl. 151, 143
  • 2006
  • At. Nucl. 56, 346
  • 1993
SLAC-265, Stanford Linear Accelerator Center
  • 1985
The quantum theory of radiation
Nucl. Inst. Meth. A460
  • Nucl. Inst. Meth. A460
  • 2001
Proc. 26th Intl. Cosmic Ray Conference
  • Proc. 26th Intl. Cosmic Ray Conference
  • 1999
Astropart. Phys
  • Astropart. Phys
  • 2003
Proc. Suppl. 151B
  • Proc. Suppl. 151B
  • 2006