CP asymmetry in B →φKS in a general two-Higgs-doublet model with fourth-generation quarks

We discuss the time-dependent CP asymmetry of the decay B → φKS in an extension of the standard model with both a two Higgs doublet and additional fourth-generation quarks. We show that, although the standard model with a two Higgs doublet and the standard model with fourth-generation quarks alone are not likely to largely change the effective sin 2 β from the decay B →φKS, the model with both an additional Higgs doublet and fourth-generation quarks can easily account for the possible large negative value of sin 2 β without conflicting with other experimental constraints. In this model, additional large CP violating effects may arise from the flavor-changing Yukawa interactions between neutral Higgs bosons and the heavy fourth-generation down type quark, which can modify the QCD penguin contributions. With the constraints obtained from b →s anti ss processes such as B →Xs γ and ΔmBs0, this model can lead to an effective sin 2 β as large as - 0.4 in the CP asymmetry of B →φKS. (orig.)