Reducing theoretical uncertainties inmbandλ1

We calculate general moments of the lepton energy spectrum in inclusive semileptonic $\overrightarrow{B}{X}_c\mathcal{l}\overline{\nu }$ decay. Moments which allow the determination of $m_b^{1S}$ and ${\lambda }_1$ with theoretical uncertainties $\Delta m_b^{1S}\sim 0.04\mathrm{GeV}$ and $\Delta {\lambda }_1\sim 0.05{\mathrm{GeV}}^2$ are presented. The short distance $1S$ mass is used to extract a mass parameter free of renormalon ambiguities. Moments which are insensitive to $m_b$ and ${\lambda }_1$ and therefore test the size of the ${1/m}_b^3$ matrix elements and the validity of the OPE are also presented. Finally, we give an expression for the total branching ratio with a lower cut on the lepton energy, which allows one to eliminate a source of model dependence in current determinations of $|V_{\mathrm{cb}}|$ from $\overrightarrow{B}{X}_c\mathcal{l}\overline{\nu }$ decay.