New Dipole Penguin Contribution to K --> pi pi decays

TL;DR

This paper introduces a new dipole penguin operator in K to pi pi decays, showing it enhances the standard Q_6 contribution by about 5%, impacting CP violation and decay amplitudes.

Contribution

It identifies a novel off-shell dipole penguin operator and demonstrates its bosonisation equivalence to the standard Q_6 operator, expanding the theoretical framework.

Findings

New dipole penguin operator contributes ~5% to Q_6.

The operator affects CP-violating ratio epsilon'/epsilon.

It significantly influences the Delta I = 1/2 decay amplitude.

Abstract

We point out that the standard chromomagnetic penguin dipole operator has a counterpart corresponding to off-shell momenta for external quarks. By employing the chiral quark model, we show that this new dipole penguin operator has the same bosonisation as the standard Q_6 operator. Accordingly, this new operator enlarges by ~ 5 % the referent Q_6 contribution, which gives the dominant contribution to the CP-violating ratio epsilon'/epsilon and also gives an important contribution to the Delta I = 1/2 amplitude.