[1] Sun Yat Sen Univ, Sch Phys & Astron, Zhuhai Campus, Zhuhai 519082, Peoples R China
[2] Hong Kong Univ Sci & Technol, Inst Adv Study, Kowloon, Clear Water Bay, Hong Kong, Peoples R China
[3] Univ Wisconsin, Dept Phys, Madison, WI 53706 USA
[4] Univ Warsaw, Inst Theoret Phys, Fac Phys, Ul Pasteura 5, PL-02093 Warsaw, Poland