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Abundance of primary protons at (1–3)×1015 eV inferred from a simulation of extensive air showers with γ-ray families

M. Shima, To. Saito, M. Sakata, and Y. Yamamoto

K. Kasahara and T. Yuda

S. Torii

N. Hotta

  • Department of Physics, Konan University, Kobe, Japan

  • Institute for Cosmic-Ray Research, University of Tokyo, Tanashi, Tokyo, Japan

  • Faculty of Engineering, Kanagawa University, Yokohama, Japan

  • Department of Physics, Faculty of Education, Utsunomiya University, Utsunomiya, Japan

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Phys. Rev. D 39, 1275 – Published 1 March, 1989

DOI: https://doi.org/10.1103/PhysRevD.39.1275

Abstract

A Monte Carlo simulation of extensive air showers (EAS’s) was done under a particle-interaction model and was compared with the EAS’s accompanied by γ-ray and hadronic families with total energy JEγ,H greater than 10 TeV obtained in the Mt. Norikura experiment (2780 m above sea level). The strong correlation between the shower size Ne of EAS’s with family and the primary energy, E0, was obtained from the simulation as E0/Ne=(2.0−0.7+2.7) GeV with 95% width. The flux of the EAS’s with family is sensitive to the chemical composition, especially to the fraction of protons in the primary cosmic-ray particles. The fraction of protons is inferred to be (20±6)% and (23±9)%, with one standard deviation (1σ), at energy (1.4−0.5+1.9)×1015 eV and (2.8−1.0+3.8)×1015 eV with 95% confidence interval, respectively, under the assumption of increasing cross section σp−air∝E0.055 and approximate Feynman scaling in the fragmentation region. These values are in agreement with the values obtained from other mountain emulsion-chamber experiments within 2σ. The proton fraction thus obtained, around 20%, is much less than the normal abundance (∼40%) expected from direct observations at lower energies around 1012 eV.

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Phys. Rev. D 39, 1275– Published 1 March, 1989
  • Received 12 October 1988

© 1989 American Physical Society

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