Cosmic ray composition studies through the Gerasimova-Zatsepin effects of heavy nuclei at LAAS
01 Sep 2011
1Dept. of Fundamental Science, Okayama University of Science, Okayama 700-0005, Japan
2Kawasaki Medical School, Kurashiki 701-0192, Japan
3Nara University of Industry, Nara 636-8503, Japan
4Yonago National College of Technology, Tottori 683-8502, Japan
5Kinki University, Osaka 577-8502, Japan
6Hirosaki University, Hirosaki 036-8561, Japan
7Dept. of Information and Computer Engineering, Okayama University of Science, Okayama 700-0005, Japan
8Okayama Shoka University, Okayama 700-8601, Japan
9Kochi University, Kochi 780-8520, Japan
10Ashikaga Institute of Technology, Ashikaga 326-8558, Japan
Abstract. Extensive air showers (EASs) originated from primary cosmic ray energies above 1015 eV have been measured at multiple EAS observatories deployed in Japan since Sept. 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 to provide the UTC time stamp for each EAS event within a few μs 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° respectively, were selected and their angular distances from the solar direction and the lunar direction were examined. The data were compared with numerical GZ probability as a function of arrival directions of cosmic ray nuclei. Consequently, significant excesses of these events in the solar direction as expected in the numerical prediction of GZ effects were not found. We however found that the deficiencies of EAS pairs in the lunar direction, but its deviation is not significant.