Lattice extraction of K→ππ amplitudes to O(p⁴) in chiral perturbation theory

We show that the lattice calculation of K→ππ and ε′ / ε amplitudes for (8,1) and (27,1) operators to O(p⁴) in chiral perturbation theory is feasible when one uses K→ππ computations at the two unphysical kinematics allowed by the Maiani-Testa theorem, along with the usual (computable) two- and three-point functions, namely K→0, K→π (with-momentum), and K-K̄. Explicit expressions for the finite logarithms emerging from our O(p⁴) analysis to the above amplitudes are also given.