The depth of maximum shower development and its fluctuations: cosmic ray mass composition at E0≥1017 eV S. P. Knurenko and A. Sabourov Yu. G. Shafer Institute for Cosmophysical Research and Aeronomy, 31 Lenin Ave., 677980 Yakutsk, Russia
Received: 15 Oct 2010 – Revised: 26 Jan 2011 – Accepted: 30 Jan 2011 – Published: 04 Jul 2011
Abstract. We present new data on Cherenkov light observations obtained during 1994–2009 period, after a modernization of the Yakutsk EAS array. A complex analysis of xmax and its fluctuations σ(xmax) was performed in a wide energy range. With the new data, according to QGSJet II model, an estimation was made of cosmic rays mass composition for E0~1017–3×1019 eV. The result points towards a mixed composition with a large portion of heavy nuclei at E0~1017 eV and the dominance of light nuclei at E0~1019 eV. The analysis of σxmax energy dependence for the same energies qualitatively confirms this result. A shape of xmax distribution at fixed energy 1018 eV is analysed to make more precise conclusion on cosmic ray mass composition.
Citation: Knurenko, S. P. and Sabourov, A.: The depth of maximum shower development and its fluctuations: cosmic ray mass composition at E0≥1017 eV, Astrophys. Space Sci. Trans., 7, 251-255, doi:10.5194/astra-7-251-2011, 2011.