ϵ _K and ϵ′/ϵ in a diquark model

Based on the calculations using the lattice QCD by the RBC-UKQCD collaboration and a large N _c dual QCD, the resulting ϵ′/ϵ, which is less than the experimental data by more than a 2σ in the standard model (SM), suggests the necessity of a new physics effect. In order to complement the insufficient ϵ′/ϵ, we study the extension of the SM with a colored scalar in a diquark model. In addition to the pure diquark box diagrams, it is found that the box diagrams with one W-boson and one diquark, ignored in the literature, play an important role in the ΔS = 2 process. The mass difference between K _L and K _S in the diquark model is well below the current data, whereas the Kaon indirect CP violation ϵ _K gives a strict constraint on the new parameters. Three mechanisms are classified in the study of ϵ′/ϵ. They include a tree-level diagram, QCD and electroweak (EW) penguins, and chromomagnetic operators (CMOs). Taking the Kobayashi-Maskawa phase as the unique CP source, we analyze each contribution of the three mechanisms in detail and conclude that with the exception of QCD and EW penguins, the tree and CMO effects can singly enhance ϵ′/ϵ to be of O(10 ⁻³ ), depending on the values of the free parameters, when the bound from ϵ _K is satisfied.