New dipole penguin contribution to K→ππ decays

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 Q6 operator. Accordingly, this new operator enlarges by ∼5% the referent Q6 contribution, which gives the dominant contribution to the CP-violating ratio ε′/ε and also gives an important contribution to the ΔI=1/2 amplitude.