R. U. Abbasi et al. 2005 ApJ 622 910 doi:10.1086/427931
A Study of the Composition of Ultra-High-Energy Cosmic Rays Using the High-Resolution Fly's Eye
FREER. U. Abbasi1, T. Abu-Zayyad1, G. Archbold1,2, R. Atkins1, J. Bellido3, K. Belov1, J. W. Belz4, S. BenZvi5, D. R. Bergman6, J. Boyer5, G. W. Burt1, Z. Cao1, R. Clay3, B. M. Connolly5, B. Dawson3, W. Deng1, Y. Fedorova1, J. Findlay1, C. B. Finley5, W. F. Hanlon1, G. A. Hughes6, P. Huntemeyer1, C. C. H. Jui1, K. Kim1, M. A. Kirn4, B. Knapp5, E. C. Loh1, M. M. Maetas1, K. Martens1, G. Martin7, N. Manago8, E. J. Mannel5, J. A. J. Matthews7, J. N. Matthews1, A. O'Neill5, L. Perera6, K. Reil1, R. Riehle1, M. D. Roberts7, M. Sasaki8, M. Seman5, S. R. Schnetzer6, K. Simpson3, J. D. Smith1, R. Snow1, P. Sokolsky1, C. Song5, R. W. Springer1, B. T. Stokes1, J. R. Thomas1, S. B. Thomas1, G. B. Thomson6, S. Westerhoff5, L. R. Wiencke1 and A. Zech6 (The High Resolution Fly's Eye Collaboration)
Show affiliationsThe composition of ultra-high-energy cosmic rays is measured with the High Resolution Fly's Eye cosmic-ray observatory data using the Xmax technique. Data were collected in stereo between 1999 November and 2001 September. The data are reconstructed with well-determined geometry. Measurements of the atmospheric transmission are incorporated in the reconstruction. The detector resolution is found to be 30 g cm-2 in Xmax and 13% in energy. The Xmax elongation rate between 1018.0 and 1019.4 eV is measured to be 54.5 ± 6.5 
± 4.5 
g cm-2 per decade. This is compared with predictions using the QGSJet01 and SIBYLL 2.1 hadronic interaction models for both protons and iron nuclei. CORSIKA-generated extensive air showers are incorporated directly into a detailed detector Monte Carlo program. The elongation rate and the Xmax distribution widths are consistent with a constant or slowly changing and predominantly light composition. A simple model containing only protons and iron nuclei is compared with QGSJet and SIBYLL. The best agreement between the model and the data is for 80% protons for QGSJet and 60% protons for SIBYLL.
- Subject headings
acceleration of particles; cosmic rays; large-scale structure of universe
- Dates
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Issue 2 (2005 April 1)
Received 2004 July 29, accepted for publication 2004 December 8
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A Study of the Composition of Ultra-High-Energy Cosmic Rays Using the High-Resolution Fly's Eye
R. U. Abbasi et al. 2005 ApJ 622 910
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