Perturbative QCD analysis of $B(B\to Xl\bar{\nu })$, charm yield $<n_c>$ in B decay, and $\tau ({\Lambda }_b)/\tau (B_d)$

Abstract

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.

Comments: 13 pages in a latex file, numerical results are revised, We obtain $B(B\to Xl\bar{\nu })=10.16$, $<n_c>=1.17$, $\tau ({\Lambda }_b)/\tau (B_d)=0.78$, and the correct absolute decay widths of the $B$ meson and of the ${\Lambda }_b$ baryon