pi K scattering in full QCD with domain-wall valence quarks

We calculate the {pi}{sup +}K{sup +} scattering length in fully-dynamical lattice QCD with domain-wall valence quarks on MILC lattices with rooted staggered sea-quarks at a lattice spacing of b=0.125 fm, lattice spatial size of L=2.5 fm and at pion masses of m{sub {pi}}{approx}290, 350, 490 and 600 MeV. The lattice data, analyzed at next-to-leading order in chiral perturbation theory, allows an extraction of the full {pi}K scattering amplitude at threshold. Extrapolating to the physical point gives m{sub {pi}}a{sub 3/2}=-0.0574{+-}0.0016{sub -0.0058}{sup +0.0024} and m{sub {pi}}a{sub 1/2}=0.1725{+-}0.0017{sub -0.0156}{sup +0.0023} for the I=3/2 and I=1/2 scattering lengths, respectively, where the first error is statistical and the second error is an estimate of the systematic due to truncation of the chiral expansion.