The kaon B-parameter from unquenched mixed action lattice QCD

Understand

We present a preliminary calculation of B_K using domain-wall valence quarks and 2+1 flavors of improved staggered sea quarks.

• Both the size of the residual quark mass, which measures the amount of chiral symmetry breaking, and of the mixed meson splitting Delta_mix, a measure of taste-symmetry breaking, show that discretization effects are under control in our mixed action lattice simulations.
• We show preliminary data for pseudoscalar meson masses, decay constants and B_K.
• We discuss general issues associated with the chiral extrapolation of lattice data, and, as an example, present a preliminary chiral and continuum extrapolation of f_pi.