Searching for cosmic ray nuclei above the KNEE energies through the Gerasimova-Zatsepin effect with the LAAS experiments

Multiple and parallel cosmic rays originated from primary cosmic ray nuclei with energies above 10eV such as due to Gerasimova-Zatsepin(GZ) effect have been searched at multiple extensive air shower (EAS) observatories scattered in Japan since 1996. Each EAS array has a GPS-disciplined 10 MHz oscillator to provide the UTC time synchronization for each EAS event within a few μs accuracies. In data analysis, EAS pairs whose time differences were less than 5 ms were selected and their angular distances from the solar direction were examined in term of local solar time. The data were compared with numerical GZ probability as a function of arrival directions of cosmic ray nuclei.