B0-(B)over-bar-0 mixing in quenched lattice QCD -: art. no. 014506

We present our results of lattice calculations of B parameters, which parametrize DeltaB=2 transition amplitudes together with the leptonic decay constant. Calculations are made in the quenched approximation at beta=5.7, 5.9, 6.0 and 6.1, using NRQCD action for heavy quarks and the O(a)-improved Wilson action for light quarks. The operators are perturbatively renormalized including the correction of O(alpha(s)/(aM)(m)) (mgreater than or equal to0). We examine the scaling behavior of B parameters, and discuss the systematic uncertainties based on the results with several different truncations of higher order terms in 1/M and alpha(s) expansions. We find B-Bd(m(b))=0.84(3)(5), B-Bs/B-Bd=1.020(21)((+15)(-16))((+5)(-0)) and B-Ss(m(b))=0.85(1)(5)((+1)(-0)) in the quenched approximation. The errors represent statistical and systematic errors as well as the uncertainty in the determination of strange quark mass.