| 摘 要： | We present the first study of CP asymmetry in Λb →Λ  decay when a new weak phase comes through the extension of three-generation standard model to the four-generation standard model. Taking  =0.01,0.02,0.03 with phase {60°-120°}, which is consistent with the rate and the Bs mixing parameter ΔmBs, we find out that CP asymmetry is quite sensitive to the existence of fourth generation. It can serve as a good tool to search for new physics effects, in particular, to search for the fourth generation quarks (t', b') via their indirect manifestations in loop diagrams.
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