[1] Seoul Natl Univ, Dept Phys & Astron, KNRC, Seoul 151742, South Korea
[2] Ctr Saclay, CEA, Irfu, SPP, F-91191 Gif Sur Yvette, France
[3] Astroparticule & Cosmol APC, F-75205 Paris 13, France
[4] Inst High Energy Phys, Beijing 100049, Peoples R China