[1] Univ Tokyo, CNS, Wako Branch, 2-1 Hirosawa, Wako, Saitama 3510198, Japan
[2] Inst Phys, VAST, Hanoi, Vietnam
[3] Adv Sci Res Ctr, JAEA, Tokai, Ibaraki, Japan
[4] Kyushu Univ, Dept Phys, Fukuoka, Japan
[5] Tohoku Univ, Dept Phys, Sendai, Miyagi, Japan
[6] Univ Tsukuba, Tsukuba, Ibaraki, Japan
[7] Yamagata Univ, Dept Phys, Yamagata, Japan
[8] McMaster Univ, Dept Phys, Hamilton, ON, Canada
[9] Univ Catania & INFN LNS, Dipartimento Fis Astron, Catania, Italy
[10] Seoul Natl Univ, Dept Phys, Seoul, South Korea
[11] Ewha Womans Univ, Seoul, South Korea
[12] Inst Modern Phys, Lanzhou, Peoples R China
[13] Chung Ang Univ, Dept Phys, Seoul, South Korea
[14] Max Planck Inst Astrophys, D-85748 D- Garching, Germany