1. Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
2. Theoretical Physics Division, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
3. University of Chinese Academy of Sciences, Beijing 100049, China
4. CAS Key Laboratory for Researches in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei 230026, China
5. Interdisciplinary Center for Theoretical Study, University of Science and Technology of China, Hefei 230026, China
6. National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China
7. Institute of Cosmology & Gravitation, University of Portsmouth, Portsmouth PO1 3FX, UK
8. Department of Astronomy, School of Physics, Peking University, Beijing 100871, China
9. Physics Department, Stanford University, Stanford, CA 94305, USA