Perturbative QCD analysis of $B(B\to Xl\bar{\nu})$, charm yield $<n_c>$   in B decay, and $\tau (\Lambda_b)/\tau (B_d)$
  We apply perturbative QCD factorization theorems to inclusive heavy hadron decays, and obtain simultaneously a low semileptonic branching ratio $B(B\to Xl\bar{\nu})=10.16%$, the average charm yield $<n_c>=1.17$ per $B$ decay, a small lifetime ratio $\tau(\Lambda_b)/\tau(B_d)=0.78$, and the correct absolute decay widths of the $B$ meson and of the $\Lambda_b$ baryon. 
We-Fu Chang, Hsiang-nan Li, and Hoi-Lai Yu