fB with lattice NRQCD including O(1/mQ2) corrections

We investigate higher order effects in the nonrelativistic expansion of lattice QCD (NRQCD) 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(α) errors due to the use of the Wilson light quark action and tree-level matching, we find that the truncation error of higher order relativistic corrections are adequately small around the mass of the b quark. Simulations are carried out on a 163×32 lattice with 120 quenched gauge configurations generated with the plaquette action at β=5.8. Systematic errors and the limitation of NRQCD theory are discussed