1. RIKEN Nishina Center, RIKEN, Wako, Saitama 351-0198, Japan
2. Department of Physics, Tohoku University, Sendai 980-8578, Japan
3. Center for Nuclear Study, University of Tokyo, Wako, Saitama 351-0198, Japan
4. Department of Physics, Osaka University, Suita, Osaka 560-0034, Japan
5. Department of Physics, Rikkyo University, Toshima, Tokyo 171-8501, Japan
6. School of Environmental Science and Engineering, Kochi University of Technology, Kami, Kochi 782-8502, Japan
7. Department of Physics, Faculty of Liberal Arts and Sciences, Tokyo City University, Setagaya, Tokyo 158-8557, Japan
8. Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-747, Korea
9. National Superconducting Cyclotron Laboratory (NSCL), Michigan State University (MSU), 640 South Shaw Lane, East Lansing, MI 48824-1321, U.S.A.
10. Laboratoire de Physique Subatomique et de Cosmologie (LPSC) Grenoble, 53, Rue des Martyrs, F-38026 Grenoble Cedex, France