[Lin, H.; Xiao, L.; Guo, D.; Zhou, W.] Cent China Normal Univ, Dept Phys, Wuhan 430079, Hubei, Peoples R China.
[Sun, Q.; Gong, D.; Ye, J.; Liu, C.; Liu, T.] Southern Methodist Univ, Dept Phys, Dallas, TX 75275 USA.
[Hou, S.] Acad Sinica, Inst Phys, Taipei 11529, Taiwan.
[Yang, D.] Univ Sci & Technol China, State Key Lab Particle Detect & Elect, Hefei 230026, Anhui, Peoples R China.