1. AMO Physics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
2. Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
3. Department of Physics, Rikkyo University, Tokyo 171-8501, Japan
4. Université de Lyon, F-69003 Lyon; Université Lyon 1, Villeurbanne; and CNRS/IN2P3, UMR5822, Institut de Physique Nucléaire de Lyon, F-69622 Villeurbanne, France
5. Accelerator Laboratory, KEK, Tsukuba, Ibaraki 305-0801, Japan
6. Department of Nuclear Engineering, Kyoto University, Kyoto 615-8540, Japan