1. Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, P. R. China
2. University of the Chinese Academy of Sciences, Beijing 100080, P. R. China
3. School of Physical Science and Technology, ShanghaiTech University, Shanghai 201203, P. R. China
4. Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA
5. Laboratori Nazionali del Sud, INFN, via Santa Sofia, 62, 95123 Catania, Italy
6. School of Physics and Information Technology, Shaanxi Normal University, Xi’an 710119, Shaanxi, P. R. China
7. Institute of Modern Physics, Department of Nuclear Science and Technology, Fudan University, Shanghai 200433, P. R. China