[Xia, Kelin] Nanyang Technol Univ, Sch Phys & Math Sci, Div Math Sci, Singapore 637371, Singapore.
[Xia, Kelin] Nanyang Technol Univ, Sch Biol Sci, Singapore 637371, Singapore.
[Li, Zhiming] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Hubei, Peoples R China.
[Li, Zhiming] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Hubei, Peoples R China.
[Mu, Lin] Oak Ridge Natl Lab, Comp Sci & Math Div, Oak Ridge, TN 37831 USA.