1. Department of Electrical Engineering and Bioscience, Waseda University, Tokyo, Japan
2. Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
3. Graduate School of Information Science and Technology, Hokkaido University, Sapporo, Japan
4. Chubu Electric Power Company, Nagoya, Japan
5. M Research Center for Nuclear Physics, Osaka University, Osaka, Japan