Simultaneous and multiple EAS Events due to the Gerasimova-Zatsepin Effect with the LAAS Experiments

We have measured extensive air showers (EAS) with primary cosmic ray energies above PeV at multiple EAS observatories deployed in Japan since 1996. Each array has been located on the rooftops of buildings in the university campus, and has a GPS-disciplined 10 MHz oscillator to provide UTC time stamps for each EAS event with microsecond accuracies. We have carried out a search for simultaneous and parallel EAS events at multiple EAS sites, such as Gerasimova-Zatsepin events, by comparing the EAS arrival time stamp and directions between long baseline EAS arrays. We selected EAS pairs for which the time difference and angular distance were less than 15 deg. and 5 msec respectively and then examined the angular distances of these events from the solar and lunar directions. Consequently, we conclude that we do not find any excesses of these events in the solar direction so far, as expected in the theoretical prediction of GZ effects. We found deficiencies of EAS pairs in the lunar direction, but its deviation is not significant.