New Possibility of Solving the Problem of Lifetime Ratio τ (Λ_b) / τ (B_d)

We discuss the problem of the large discrepancy between the observed lifetime ratio of $\Lambda_b$ to $B_d$ and the theoretical prediction obtained by the heavy quark effective theory. A new possibility of solving this problem is proposed from the viewpoint of operator product expansion and the lifetime ratio of $\Omega_b$ to $B_d$ is predicted.