K+ → π+π0 decays at next-to-leading order in the chiral expansion on finite volumes

We present the ingredients for determining K+ → π+π0 matrix elements via the combination of lattice QCD and chiral perturbation theory (χPT). By simulating these matrix elements at unphysical kinematics, it is possible to determine all the low-energy constants (LECs) for constructing the physical K+ → π+π0 amplitudes at next-to-leading order (NLO) in the chiral expansion. In this work, the one-loop chiral corrections are calculated for arbitrary meson four-momenta, in both χPT and quenched χPT (qχPT), and the finite-volume effects are studied.