We present our recent results for the B-parameters, which parameterize the \Delta B=2 transition amplitudes. Calculations are made in quenched QCD at \beta=5.7, 5.9, and 6.1, using NRQCD for heavy quark and the O(a)-improved action for light quark. The operators are perturbatively renormalized including corrections of O(\alpha_s/am_Q). We examine scaling behavior of the B-parameters in detail, and discuss the systematic uncertainties using scatter of results with different analysis procedures adopted. As a result, we find B_{B_d}(m_b)=0.84(2)(8), B_{B_s}/B_{B_d}=1.017(10)(^{+4}_{-0}) and B_{S_s}(m_b)=0.87(1)(9)(^{+1}_{-0}) in the quenched approximation.
@article{arxiv.hep-lat/0010089,
title = {B^0-\bar{B}^0 mixing with quenched lattice NRQCD},
author = {JLQCD Collaboration and N. Yamada and S. Aoki and R. Burkhalter and M. Fukugita and S. Hashimoto and K-I. Ishikawa and N. Ishizuka and Y. Iwasaki and K. Kanaya and T. Kaneko and Y. Kuramashi and M. Okawa and T. Onogi and S. Tominaga and N. Tsutsui and A. Ukawa and T. Yoshié},
journal= {arXiv preprint arXiv:hep-lat/0010089},
year = {2009}
}