Improved Bilinears in Unquenched Lattice Qcd *

It is important to pursue simulations with Wilson-like fermions, despite their greater computational cost than staggered fermions, because one avoids the theoretical uncertainty associated with taking roots of the fermion determinant. One drawback with Wilson fermions is that they lead to discretization errors of O(a), slowing the approach to the continuum. This can be ameliorated using anO(a) improved action, with the relevant improvement coefficient, cSW , determined non-perturbatively using the method of Ref. [1]. One also wants to improve the matrix elements of operators, and a technique for doing so has been worked out for non-singlet quark bilinears with degenerate dynamical quarks [1]. Here we sketch the generalization of this improvement program to the realistic case of three non-degenerate dynamical quarks, and to all bilinears, including flavor singlets. The inclusion of flavor singlets is a necessary part of the technique, and is furthermore of phenomenological interest. This study is the completion of the work presented in [2], which was incomplete and partly incorrect. Many details must necessarily be skipped in this short writeup; a complete discussion, including the generalization to two and four flavors, will be presented in [3]. We assume that the following steps in the improvement program have already been taken: (1) cSW and cA have been determined by enforcing the PCAC relation for non-singlet axial currents with degenerate quarks [1]; (2) κc is known from