  A measurement of the hadron energy spectrum in inclusive semileptonic $B$
decays is proposed as a viable method for extracting $|V_{ub}|$. Compared to
the traditional energy spectrum of the charged lepton, the hadron energy
spectrum exhibits kinematical advantages such as a wider energy window and a
larger signal branching fraction. It is emphasized that the hadron energy
spectrum method is most suited for symmetric $B$ factories, such as CLEO. The
hadron energy distribution is calculated in the approach of the Altarelli et
al. model and of the heavy-quark effective field theory. In both methods,
perturbative QCD corrections, the Fermi motion of the $b$-quark in the
$B$-meson, and the recoil momentum of the $B$-meson (stemming from the
$\Upsilon(4S)$ resonance) are taken into account. We have found excellent
agreement between the spectra calculated in both methods, especially in the
relevant kinematical region below the charmed meson threshold. The theoretical
error to $|V_{ub}|$, which is dominated by the uncertainty of the $b$-quark
mass, is estimated to be at the $\pm 12 \%$ level.

High Energy Physics - Phenomenology