Measurement of the cosmic ray spectrum above 10^16 eV energy regions with compact EAS arrays at LAAS

MATSUMOTO Hiroki, IYONO Atsushi, YAMAMOTO Isao , OKEI Kazuhide, TSUJI Shuhei, NAKATSUKA Takao , OHARA Soji,TAKAHASHI Nobusuke, OCHI Nobuaki

Extensive air showers (EASs) produced by primary cosmic ray energies above the KNEE energies have been observed at multiple EAS observatories simultaneously scattered in Japan since 1996. The typical EAS array has been located at the rooftop of the buildings in the university campus, and has GPS disciplined 10
MHz oscillator which provides the UTC time stamp for each EAS event within a few ms accuracies. Searching for simultaneous and parallel EAS events at multiple EAS observatories due to Gerasimova-Zatsepin (GZ) effects have been carried out by comparing EAS arrival time stamps and directions detected by several baseline
combinations of EAS arrays. The EAS pairs whose time difference and angular distance were less than 5 ms and less than 15 degree respectively, were selected and their angular distances from the solar direction and the lunardirection were examined. Consequently, significant excesses of these events in the solar direction as expected in the numerical prediction of GZ effects were not found.

Proceedings of 33RD INTERNATIONAL COSMIC RAY CONFERENCE