[1] Liaoning Normal Univ, Dept Phys, Dalian 116029, Peoples R China
[2] Louisiana State Univ, Dept Phys & Astron, Baton Rouge, LA 70803 USA
[3] Peking Univ, Dept Phys, Beijing 100871, Peoples R China
[4] Peking Univ, Natl Key Lab Nucl Phys & Technol, Beijing 100871, Peoples R China
[5] Ctr Theoret Nucl Phys, Natl Lab Heavy Ion Accelerator, Lanzhou 730000, Peoples R China