CP Violation inΛb →Λ

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 therate 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.