Analysis of Bd→ψ KS CP Asymmetry in a Flavour Changing Z'' Model

According to the recent experimental data, the time-dependent CP asymmetry SφKs for Ba → CKs decay might still be inconsistent with the standard model （SM） expectations. We try to understand the anomaly with a Z＇ model associated with flavour changing neutral currents （FCNCs） at the tree level. We find that （i） if neglecting the contributions from the right-handed flavour changing coupling Bsb^R and setting ξ^LL = ξ^LR =ξ and ξ^LL = ξ, ξ^LR = 0, we may obtain 0.01 〈ξ 〈 0.014, 0.0175 〈ξ〈 0.0205, 0.021 〈 ξ 〈 0.0255 and 0.004 〈 ξ 〈 0.008, 0.018 〈ξ 〈 0.028, 0.042 〈ξ〈 0.048 for the Bd → φKs decay, respectively; （ii） if considering the contributions coming from Bsb^R and setting ξ^LL = ξ^RL= ξ^LR = ξ,ξ^LR =ξ^RR=0, we can obtain 0.005 〈 ξ 〈 0.075, 0.0085 〈 ξ 〈 0.0105, 0.011 〈 ξ 〈 0.013 and 0.0125 〈 ξ 〈 0.0177, 0.0224 〈 ξ 〈 0.025. These results are consistent with the constraints and the assumptions in some literature.