$D_s$ Lifetime, $m_b$, $m_c$ and $\mathrm{\mid }{V}_{cb}\mathrm{\mid }$ in the Heavy Quark Expansion

We present some straightforward applications of the QCD heavy quark expansion, stated in previous papers [1-3], to the inclusive widths of heavy flavour hadrons. We address the question of the $D_s$ lifetime and argue that – barring Weak Annihilation (WA) – $\tau (D_s)$ is expected to exceed $\tau (D^0)$ by several percent; on the other hand WA could provide a difference of up to $10÷20\mathrm{\%}$ of {\it any} sign. We extract $m_c$, $m_b$ and $\mathrm{\mid }{V}_{cb}\mathrm{\mid }$ from $\mathrm{\Gamma }\text{ind}SL(D^{+})$ and $\mathrm{\Gamma }\text{ind}SL(B)$. The values of the quark masses are somewhat higher, but compatible with estimates from QCD sum rules; we obtain $\mathrm{\mid }{V}_{cb}\mathrm{\mid }\simeq 0.043$ for $\tau (B)=1.4$ psec and $B{R}_{SL}(B)=10.5$% . We discuss the associated uncertainties in the $1\mathrm{/}{m}_Q$ expansion as well as some consequences for other electroweak decays.