1. KAGRA Observatory, Institute for Cosmic Ray Research, University of Tokyo, 238 Higashi Mozumi, Kamioka, Hida, Gifu 506-1205, Japan
2. Department of Applied Physics, Fukuoka University, Jonan, Nanakuma, Fukuoka 814-0180, Japan
3. Institut für Kernphysik, Technische Universität Darmstadt Schlossgartenstrasse 9, D-64289 Darmstadt, Germany
4. Division of Theoretical Astronomy, National Astronomical Observatory of Japan (NAOJ), 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan