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

R. U. Abbasi (Author), T. Abu-Zayyad (Author), M. Al-Seady (Author), M. Allen (Author), J. F. Amman (Author), R. Anderson (Author), G. Archbold (Author), K. Belov (Author), J. W. Belz (Author), D. R. Bergman (Author), S. A. Blake (Author), J. P. Lundquist (Author)

Abstract

We report studies of ultrahigh-energy cosmic-ray composition via analysis of depth of air shower maximum (Xmax), 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⟨Xmax⟩/d[log(E)] of 47.9 ± 6.0 (stat) ± 3.2 (syst) g/cm^2/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 4×10^18 eV.

Keywords

cosmic rays;energy spectrum;telescope array;ultra high energy;

Data

Language:	English
Year of publishing:	2010
Typology:	1.01 - Original Scientific Article
Organization:	UNG - University of Nova Gorica
UDC:	524
COBISS:	12843779
ISSN:	0031-9007
Views:	2063
Downloads:	0
Average score:	0 (0 votes)
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Other data

URN:	URN:SI:UNG
Type (COBISS):	Not categorized
Pages:	str. 161101-1- 161101-5
Issue:	ǂVol. ǂ104
Chronology:	Apr. 2010
DOI:	10.1103/PhysRevLett.104.161101
ID:	11591950