[en] The balloon experiment of long duration using large and heavy detectors is required to observe the new particles produced by superhigh energy interaction. Six emulsion chambers were exposed to cosmic ray in the experiment of balloon flight by Australia-Japan collaboration. Exposure continued 32.5 hours, then the emulsion chambers were recovered. The cosmic ray with incident energy of 10 - 20 TeV was observed, and the increase of the production rate of new particles is expected by this increase of energy. The tracks of the new particles with lifetime of 10^-15 - 10^-12 s were able to be detected in the emulsion chambers. To date, 49 interaction events of protons, α particles and heavy nuclei were analyzed, and 2 events among them were accompanied by the pair production of new elementary particles. The present analysis shows that the production rate of new particles is 1 - 5% in the 10 - 20 TeV energy range, and this value is about ten times as large as that at 400 GeV. The mean lifetime and the distribution of transverse momentum of X-particles were obtained, and the results show that the mean lifetime and transverse momentum are (8 - 9) x 10^-13 s and 1.6 +- 0.5 GeV/C, respectively. (Yoshimori, M.)