Direct CP Violation in K-decay and Minimal Left-Right Symmetry Scale
  We calculate the new contribution to the direct CP-violation parameter $\epsilon'$ in $K\to \pi\pi$ decay in the minimal left-right symmetric model with the recently-obtained right-handed quark Cabibbo-Kobayashi-Maskawa mixing. We pay particular attention to the uncertainty in the hadronic matrix element of a leading four-quark operator $O^{LR}_-$. We find that it can be related to the standard model electromagnetic penguin operator $O_8$ through $SU(3)_L \times SU(3)_R$ chiral symmetry. Using the lattice and large $N_c$ calculations, we obtain a robust constraint on the minimal left-right symmetric scale $M_{W_R}>5$ TeV from the experimental data on $\epsilon'$. 
Panying Chen, Hongwei Ke, Xiangdong Ji