Unusually penetrating particle detected by balloon-borne emulsion chamber

M. Ichimura, E. Kamioka, M. Kitazawa, T. Kobayashi, T. Shibata, S. Somemiya, M. Kogawa, S. Kuramata, H. Matsutani, T. Murabayashi, H. Nanjyo, Z. Watanabe, H. Sugimoto, K. Nakazawa

Research output: Contribution to journalArticlepeer-review

58 Citations (Scopus)


One example of an unusual particle track has been recorded in an emulsion chamber exposed to cosmic rays on a ballon at the atmospheric depth 11.7 g/cm2. The particle arrived at the chamber with Z/β=40±2 and β≳0.8. What is extraordinary with this particle is its arrival zenith angle, 87.4°, which amounts to a traversed atmospheric thickness ∼200 g/cm2. The anomalous nature of the present track "ET" (exotic track) is demonstrated through the difficulties in reconciling it with the explanation that it is due to an ordinary ultra-heavy cosmic-ray nucleus.

Original languageEnglish
Pages (from-to)843-852
Number of pages10
JournalIl Nuovo Cimento A
Issue number6
Publication statusPublished - 1993 Jun 1
Externally publishedYes


  • Cosmic rays
  • Other and hypothetical particles (including tachyons)

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Nuclear and High Energy Physics
  • Astronomy and Astrophysics


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