Indications of Proton-Dominated Cosmic Ray Composition above 1.6 EeV

Indications of Proton-Dominated Cosmic Ray Composition above 1.6 EeV

We report studies of ultra-high energy cosmic ray composition via analysis of depth of airshower maximum (Xmax), for airshower 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.)...

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Veröffentlicht in:arXiv.org 2010-04
Hauptverfasser: Abbasi, R U, Abu-Zayyad, T, Al-Seady, M, Allen, M, Amman, J F, Anderson, R J, Archbold, G, Belov, K, Belz, J W, Bergman, D R, Blake, S A, Brusova, O A, Burt, G W, Cannon, C, Cao, Z, Deng, W, Fedorova, Y, Finley, C B, Gray, R C, Hanlon, W F, Hoffman, C M, Holzscheiter, M H, Hughes, G, Huentemeyer, P, Jones, B F, Jui, C C H, Kim, K, Kirn, M A, Loh, E C, Lundquist, J P, Maestas, M M, Manago, N, Marek, L J, Martens, K, Matthews, J A J, Matthews, J N, Moore, S A, O'Neill, A, Painter, C A, Perera, L, Reil, K, Riehle, R, Roberts, M, Rodriguez, D, Sasaki, N, Schnetzer, S R, Scott, L M, Sinnis, G, Smith, J D, Sokolsky, P, Song, C, Springer, R W, Stokes, B T, Stratton, S, Thomas, S B, Thomas, J R, Thomson, G B, Tupa, D, Zhang, X, Zech, A
Format: Artikel
Sprache:eng
Schlagworte:
Astronomical models
Composition
Cosmic rays
Elongation
Energy spectra
High energy astronomy
Interaction models
Physics - High Energy Astrophysical Phenomena
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Zusammenfassung:We report studies of ultra-high energy cosmic ray composition via analysis of depth of airshower maximum (Xmax), for airshower 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/cm^2/decade for energies between 1.6 EeV and 63 EeV, and are consistent with a predominantly protonic composition of cosmic rays when interpreted via the QGSJET01 and QGSJET-II high-energy hadronic interaction models. These measurements constrain models in which the galactic-to-extragalactic transition is the cause of the energy spectrum "ankle' at 4 EeV.
ISSN:2331-8422
DOI:10.48550/arxiv.0910.4184