SOME STORIES OF BRASIL-JAPAN COLLABORATION AND CHACALTAYA MOUNTAIN

An international cooperation, named Brasil-Japan Collaboration of Chacaltaya Emulsion Chamber Experiment (B-J Collaboration) exposed 2.35 × 108 m2.s, during the period 15thJun, 1962 till 10thMay, 1988. It corresponds to 22 'runs' on Cosmic Rays and in this figure are not included photosensitive material set in the lower part of the two-storied emulsion chamber. Although 3 more 'runs' occurred after 1988, they were not included either, because they were not yet properly measured and because they contain mixed Japanese and Russian films. Chacaltaya Mountain was firstly used in 1947 for 2 meson observations and π - μ decays. It was a wise choice not only for these observations but also for the B-J Collaboration and for the Alpaca Project, running at neighbouring sites. The main results observed by the B-J Collaboration are presented.

Exotic model of the cosmic ray spectrum

A detailed study of the cores of extensive air showers (EAS) at mountain level (Tien-Shan 690 g/cm2) was carried out in the hybrid experiment HADRON. An analysis of the fine structure of the EAS spectrum in the energy region1015 - 1017 (knee) showed that there are two breaks in the spectrum. Along with the previously known break at an energy of 3 · 1015 eV, a change in the slope of the EAS spectrum is observed at an energy slightly below 1017 eV. In addition the use of a large X-ray emulsion chamber (XREC) as a detector of EAS cores allowed us to obtain several new results. An abnormal scaling violation in hadron spectra for Ne ~ 107 (E0 ~ 1016 eV) means the existence of a penetrating component of non-nuclear origin. The conclusion about the non-nuclear origin of the penetrating component in the primary radiation of CR is confirmed by the data about the excess of muons in the EAS containing hadrons of maximum energies. It is assumed that the mass composition of primary cosmic radiation varies sharply at energies of 1015 - 1016 eV, where quasi-nuclei (strangelets) appear instead of nuclei. A new model of the mass composition of cosmic rays in the region of ultrahigh energies is proposed on this basis .

Emulsion chamber observations of Centauros, aligned events and the long-flying component

The cosmic ray emulsion chamber community has reported several unusual phenomena which are also relevant to experiments at the current high-energy accelerators, in particular the Fermilab Tevatron Collider and the CERN Large Hadron Collider (LHC). A summary of the ”Cosmic Rays at Mountain Altitude” workshop held at Plock (Poland, September 2010) is given.