It is pointed out that the $\mathrm{CP}$-violating phases in the $Z_4$ model with four generations are much more restricted than those in the standard Kobayashi-Maskawa model with four generations, which involve a large number of arbitrary parameters in the $\mathrm{CP}$-violating sector.

• Received 20 November 1989

DOI:https://doi.org/10.1103/PhysRevD.44.865