The kaon B-parameter from 2+1-flavor Domain-Wall-Fermion lattices

We present the final results of the RBC/UKQCD calculation of the kaon B-parameter on 2+1- flavor domain-wall fermion lattices at a?1 = 1.73(3) GeV. We simulate on two lattice volumes of about (1.8 fm)3 and (2.7 fm)3, with the lightest valence pion about on the large volume approximately 250 MeV. The light pion masses and our chiral fermion action allow us to compare lattice data to NLO chiral perturbation theory, facilitating a controlled extrapolation to the physical point. We present a final result including nonperturbative renormalization and detailed systematic errors. Our final result is BMS/K (2 GeV) = 0.524(10)(28).