  We present our calculations for the $I$ = 1/2 and 3/2 $K-\pi$ s-wave
scattering length with physical quark masses, extracted from the interaction
energy of Euclidean two-point functions. We use the domain wall fermion action
with physical quark masses at a single lattice spacing. We are specifically
interested in the systematic effects due to around-the-world terms on the
overall determination of the scattering length. We present our progress and
discuss the various systematic effects in our preliminary results.
