1. Guangdong Provincial Key Laboratory of Nuclear Science, Institute of Quantum Matter, South China Normal University, Guangzhou 510006, China
2. Key Laboratory of Quark & Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University, Wuhan 430079, China
3. School of Mathematics and Physics, China University of Geosciences, Wuhan 430074, China
4. Nuclear Science Division MS 70R0319, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA