作者机构:[1]Department of Engineering Physics, Tsinghua University, Beijing 100084, China, [2]Center for Astrophysics, Tsinghua University, Beijing 100084, China, [3]Key Laboratory of Particle Astrophysics, Institute of High Energy Physics Chinese Academy of Sciences, Beijing 100049, China, [4]Department of Physics, Tsinghua University, Beijing 100084, China
相关基金:Supported by National Basic Research Program of China (973 Program 2009CB824800)