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 — preprints:2002:ttp02-06 [2016/03/17 11:03] (current) Line 1: Line 1: + ====== 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. + ​ + |**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]] ​  | + | |