Direct CP Violation in K-decay and Minimal Left-Right Symmetry Scale

TL;DR

This paper calculates the impact of minimal left-right symmetric models on direct CP violation in K-decays, constraining the new physics scale to above 5 TeV using lattice and large N_c methods.

Contribution

It introduces a new calculation of CP violation contributions in left-right symmetric models, relating hadronic matrix elements to known operators and deriving bounds on the symmetry scale.

Findings

Left-right symmetry scale constrained to be above 5 TeV

Relates hadronic matrix elements to electromagnetic penguin operators

Provides robust bounds using lattice and large N_c calculations

Abstract

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 $\epsilon'$.