Lattice QCD with dynamical domain wall quarks

An obvious source of systematic error in numerical lattice QCD at present is the quenched approximation. Use of domain wall fermion (DWF) [1] dynamical quarks to lift this approximation is attractive because DWF preserve the flavor and chiral symmetries both on and off shell on the lattice before the continuum limit is taken. Evidently successful implementation would bring many advantages, such as detailed study of flavor-singlet meson spectrum and its relation to the U(1)A anomaly. However some recent exploratory calculations [2] on coarse lattices with cut off of a−1 < 1 GeV show the chiral symmetry is rather poorly realized: impractically large Ls ∼ 100 are necessary to bring the residual symmetry violation under control. In contrast in this work we go to a higher cutoff of a−1 ∼ 2 GeV with renormalization-group (RG) motivated gauge actions and find that the residual violation can be made sufficiently small even at Ls = 12. To cope with considerably larger demand for computing resources brought by this new approach, we introduce two improvements in the