A STUDY OF O(1 M(Q)(2)) CORRECTIONS FOR F(B) WITH LATTICE NRQCD/

We investigate higher order effects in the nonrelativistic expansion o f lattice QCD on the heavy-light meson decay constants and some other quantities in order to understand the truncation error of NRQCD. While our numerical results have large O(a) and O(alpha(s)) errors due to t he use of Wilson light quark action and the tree-level matching, we fi nd that the truncation error of higher order relativistic corrections are adequately small around the mass of the b quark. We also present a perturbatively matched results through 1-loop level without operator mixing effects.