Preliminary study of $B_B$ parameter using Lattice NRQCD
  We present the preliminary result of the calculation of $B_B$ parameter using lattice NRQCD. The calculation is performed on a $16^3 \times 48$ quenched lattice at $\beta=5.9$ with clover light quark. The use of lattice NRQCD enables us to investigate the $1/m_Q$ correction from the static limit. The observed mass dependence is well described by the vacuum saturation. 
N. Yamada, S. Hashimoto, K-I. Ishikawa, H. Matsufuru, T. Onogi and S.   Tominaga