Preliminary study of the scattering length from lattice QCD

The s-wave kaon-antikaon (K anti K) scattering length is studied by lattice QCD using pion masses mπ =330-466 MeV. Through wall sources without gauge fixing, we calculate four-point functions in the I=1 channel with the ''Asqtad''-improved staggered fermion formulation, and observe an attractive signal, which is consistent with pioneering lattice studies on potential. Extrapolating the scattering length to the physical point, we obtain, where the first error is statistical and the second is systematic. These simulations are conducted with MILC gauge configurations at lattice spacing a ∼0.15 fm. (orig.)