The K+K+ scattering length is calculated in fully-dynamical lattice QCD with domain-wall valence quarks on the MILC asqtad-improved gauge configurations with rooted staggered sea quarks. Three-flavor mixed-action chiral perturbation theory at next-to-leading order, which includes the leading effects of the finite lattice spacing, is used to extrapolate the results of the lattice calculation to the physical value of m_{K+}/f_{K+}. We find m_{K+} a_{K+K+} = -0.352 +- 0.016, where the statistical and systematic errors have been combined in quadrature.
@article{arxiv.0709.1169,
title = {The K+K+ Scattering Length from Lattice QCD},
author = {Silas Beane and Thomas Luu and Kostas Orginos and Assumpta Parreno and Martin Savage and Aaron Torok and Andre Walker-Loud},
journal= {arXiv preprint arXiv:0709.1169},
year = {2008}
}