1. Institute of High Energy Physics and Theoretical Physics Center for Science Facilities, Chinese Academy of Sciences, Beijing 100049, China
2. Institute of Physics, Academia Sinica, Taipei 115, Taiwan
3. Department of Physics, National Tsing-Hua University, Hsinchu 300, Taiwan
4. Department of Physics, National Cheng-Kung University, Tainan 701, Taiwan
5. School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China