Measurement of |Vub| near the endpoint of the electron momentum spectrum from semileptonic B-meson decays

Le résumé fourni par la source

We report measurements of partial branching fractions of inclusive charmless semileptonic B -meson decays at the endpoint of the electron momentum spectrum. The measurements are made in six overlapping momentum intervals that have lower bounds ranging from 1.9 to 2.4 GeV/ c and a common upper bound of 2.6 GeV/ c , as measured in the centre of mass frame. The results are based on a sample of 29 million B B ¯ pairs, accumulated by the Belle detector at the KEKB asymmetric e + e − collider operating on the ϒ ( 4 S ) resonance. In the momentum interval ranging from 1.9 to 2.6 GeV/ c we measure the partial branching fraction Δ B ( B → X u e ν e ) = ( 8.47 ± 0.37 ± 1.53 ) × 10 −4 , where the first error is statistical and the second is systematic. A prediction of the partial rate R = ( 21.69 ± 3.62 −1.98 +2.18 ) | V u b | 2 ps −1 in this momentum interval based on theory is calculated with input HQET parameters that have been derived from Belle's measurement of the B → X s γ photon energy spectrum , where the first error is due to the uncertainty on HQET parameters and the second error is from theory. Using both Δ B ( B → X u e ν e ) and R we find | V u b | = ( 5.08 ± 0.47 ± 0.42 −0.23 +0.26 ) × 10 −3 , where the first error is from the partial branching fraction, and the second and third errors are from uncertainties in R .

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