====== TTP02-06 Subleading shape functions in $B \to X_u \ell \bar \nu$ and the determination of $|V_{ub}|$ ======
 
 
   <hidden TTP02-06  Subleading shape functions in $B \to X_u \ell \bar \nu$ and the determination of $|V_{ub}|$ > We calculate the subleading twist contributions to the endpoint of the
 inclusive lepton energy spectrum in $B \to X_u \ell \bar\nu$. We show
 that the same two subleading twist functions that appear in the decay
 $B \to X_s \gamma$ govern the subleading effects in this decay. Using
 these results we find large ${O}(\lqcd/m_B)$ corrections to the
 determination of $|V_{ub}|$ from the endpoint of the charged lepton
 spectrum.  Using a simple model for the relevant subleading shape functions,
 we estimate the uncertainty in $|V_{ub}|$ from $\lqcd/m_b$ corrections
 to be at the $\sim 15\%$ level for a lower lepton energy cut of 2.2 GeV.
 </hidden>
|**Christian W. Bauer, Michael Luke, Thomas Mannel**  | 
|**  Phys. Lett.  B543 261-268 2002  **  |
| {{preprints:2002:ttp02-06.pdf|PDF}} {{preprints:2002:ttp02-06.ps|PostScript}} [[http://arxiv.org/abs/hep-ph/0205150|arXiv]]   |
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