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. 2010 Apr 23;104(16):161101.
doi: 10.1103/PhysRevLett.104.161101. Epub 2010 Apr 20.

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

R U Abbasi  1 , T Abu-Zayyad, M Al-Seady, M Allen, J F Amman, R J Anderson, G Archbold, K Belov, J W Belz, D R Bergman, S A Blake, O A Brusova, G W Burt, C Cannon, Z Cao, W Deng, Y Fedorova, C B Finley, R C Gray, W F Hanlon, C M Hoffman, M H Holzscheiter, D Ivanov, G Hughes, P Hüntemeyer, D Ivanov, B F Jones, C C H Jui, K Kim, M A Kirn, E C Loh, J Liu, J P Lundquist, M M Maestas, N Manago, L J Marek, K Martens, J A J Matthews, J N Matthews, S A Moore, A O'Neill, C A Painter, L Perera, K Reil, R Riehle, M Roberts, D Rodriguez, N Sasaki, S R Schnetzer, L M Scott, G Sinnis, J D Smith, P Sokolsky, C Song, R W Springer, B T Stokes, S Stratton, S B Thomas, J R Thomas, G B Thomson, D Tupa, A Zech, X Zhang; High Resolution Fly's Eye Collaboration
Affiliations

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

R U Abbasi et al. Phys Rev Lett. .

Erratum in

  • Phys Rev Lett. 2010 May 14, 104(19):199902. Ivanov, D [added]

Abstract

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<X(max)>/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 hadronic interaction models. These measurements constrain models in which the galactic-to-extragalactic transition is the cause of the energy spectrum ankle at 4x10(18) eV.

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