Acad Sinica, Inst Theoret Phys, Beijing 100080, Peoples R China
; CCAST, World Lab, Beijing 100080, Peoples R China
; Acad Sinica, Inst High Energy Phys, Beijing 100039, Peoples R China
We investigate the epsilon'/epsilon for K --> pi pi in a sequential fourth generation model. By giving the basic formulas for epsilon'/epsilon in this model, we analyze the numerical results which are dependent on m(t), and the imaginary part of the fourth CKM factor, IMV*V-t's(t'd) (or V*V-t's(t'd) and the fourth generation CKM matrix phase theta). We find that, unlike the SM, when taking the central values of all parameters for epsilon'/epsilon, the values of epsilon'/epsilon can easily fit to the current experimental data for all values of hadronic matrix elements estimated from various approaches. Also, we show that the experimental values of epsilon'/epsilon and rare K decays can provide a strong constraint on both mass and mixing of the fourth generation quark. When taking the values of hadronic matrix elements from the lattice or 1/N expansion calculations, a large region of the up-type quark mass m(t), is excluded.