[1] Shanghai Jiao Tong Univ, Inst Nat Sci, Shanghai Key Lab Particle Phys & Cosmol, Shanghai 200240, Peoples R China
[2] Shanghai Jiao Tong Univ, Ctr Astrophys & Astron, Dept Phys & Astron, Shanghai 200240, Peoples R China
[3] SUNY Buffalo, Dept Phys, HEPCOS, Buffalo, NY 14260 USA