Perturbative Renormalization Factors of Bilinear Quark Operators for Improved Gluon and Quark Actions in Lattice QCD

We calculate one-loop renormalization factors of bilinear quark operators for gluon action including six-link loops and O(a)-improved quark action in the limit of massless quark. We find that finite parts of one-loop coefficients of renormalization factors diminish monotonically as either of the coefficients c1 or c2 + c3 of the six-link terms are decreased below zero. Detailed numerical results are given, for general values of the clover coefficient, for the tree-level improved gluon action in the Symanzik approach (c1 = −1/12, c2 = c3 = 0) and for the choices suggested by Wilson (c1 = −0.252, c2 = 0, c3 = −0.17) and by Iwasaki (c1 = −0.331, c2 = c3 = 0 and c1 = −0.27, c2 + c3 = −0.04) from renormalization-group analyses. Compared with the case of the standard plaquette gluon action, finite parts of one-loop coefficients are reduced by 10–20% for the Symanzik action, and approximately by a factor two for the renormalization-group improved gluon actions. Typeset using REVTEX 1