Affiliation: | a Institute for Cosmic Ray Research, University of Tokyo, Tanashi, Tokyo 188-8502, Japan b Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan c Department of Physics, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan d Communication Systems Center, Mitsubishi Electric Corporation, Amagasaki, Hyogo 661-8661, Japan e Department of Physics and Mathematical Physics, University of Adelaide, South Australia 5005, Australia f Faculty of Science, Ibaraki University, Mito, Ibaraki 310-8521, Japan g STE Laboratory, Nagoya University, Nagoya, Aichi 464-8601, Japan |