N. Arata

A new type of nuclear interactions in the ΣEγ≳1014 eV region

Centauro‐type and Mini‐Centauro‐type events are reported and discussed. They are events in which nuclear‐active particles (i.e. hadrons which do not undergo rapid photon decays) are produced without any sign of accompanying neutral pion emission. Estimated hadron multiplicity is ∠100 for Centauro‐type and ∠15 for Mini‐Centauro‐type.Up to the present moment, 5 examples of Centauro and 13 of Mini‐Centauro have been observed in the two‐storey emulsion chambers exposed on Mt. Chacaltaya, Bolivia (5220 m above sea level).The experimental results on energy and angular distributions are in agreement with the hypothesis that this type of events occur through production and decay of a fire‐ball with a rest energy of (200∠300) GeV/c2 for Centauro and ∠30 GeV/c2 for Mini‐Centauro events.

Baryon pair production with large decay Q‐value

Events of a new type have been observed by the chacaltaya Emulsion Chamber Experiment,1,2 which can consistently be interpreted as ’’baryon’’ pair decay of a heavy intermetiate state of rest mas 20–30 GeV/c2.

Multiple meson production in the Σ Eγ≳2×1013 eV region

Cosmic‐ray‐induced unclear interactions are observed by emulsion chambers exposed on Mt. chacaltaya, Bolivia (5220m above sea level). We detect photons from nuclear interactions which occurred within the petroleum putch layer (1/3 nuclear mean free path), set 150 cm above the emulsion chamber.Photons of energy ≳100 GeV are detected in each event, the highest detected photon energy being 40TeV. 350 events are found to contain 4 or more photons, whose energy sums, ? Eγ, range from 5 TeV up to 500 TeV, and are adopted for analysis.Multiplicity‐, energy‐, angular‐, PT‐, and other related distributions of the photons are presented, comparison is made with the accelerator data, and discussions are given.