Leading effect of CP violation with four generations

In the standard model with a fourth generation of quarks, we study the relation between the Jarlskog invariants and the triangle areas in the 4×4 Cabibbo-Kobayashi-Maskawa matrix. To identify the leading effects that may probe the CP violation in processes involving quarks, we invoke small mass and small angle expansions, and show that these leading effects are enhanced considerably compared to the three-generation case by the large masses of fourth-generation quarks. We discuss the leading effect in several cases, in particular, the possibility of large CP violation in b→s processes, which echoes the heightened recent interest because of experimental hints.