Large Dimuon Asymmetry and a Non-Universal Z^′ Boson in the B_s−B_s System

Motivated by recently observed anomalously large dimuon charge asymmetry in neutral B decays reported by the D0 collaboration, we study the effects of a family of non-universal Z^′ bosons for possible solutions. The fitting results for the Z^′ parameters are presented under the constraints from the D0 result for a_sl^s and UTfit results for C_Bs and φ_Bs in two limiting scenarios for left− and right-handed b-s-Z^′ couplings. We find the couplings B_sb^L and B_sb^R are rigorously bounded but not excluded, which means that the anomalies in the B_s−B_s system could be moderated simultaneously within a non-universal Z^′ model. Numerically, a new weak phase φ_L^s ∼−60° (−80°) in scenario I or ∼30°(10°) in scenario II is crucial to moderate the large dimuon charge asymmetry.