B-0-(B)over-bar(0) mixing with quenched lattice NRQCD

We present our recent results for the B-parameters, which parameterize the DeltaB=2 transition amplitudes. Calculations are made in quenched QCD at be ta =5.7, 5.9, and 6.1, using NRQCD for heavy quark and the O(a)-improved ac tion for light quark. The operators are perturbatively renormalized includi ng corrections of O(alphas/am(Q)), We examine scaling behavior of the B-par ameters in detail, and discuss the systematic uncertainties using scatter o f results with different analysis procedures adopted. As a result, we find B-Bd(m(b)) = 0.84(2)(8), B-Ba/B-Bd = 1.017(10)((+4)(-0)) and B-Sa (m(b)) = 0.87(1)(9)((+1)(-0)) in the quenched approximation.