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Measurement of the B0 --> pi l nu Form-Factor Shape and Branching Fraction, and Determination of |Vub| with a Loose Neutrino Reconstruction Technique

B. Aubert et al.
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Abstract

We report the results of a study of the exclusive charmless semileptonic decay, B --> pi l nu, undertaken with approximately 227 million BBbar pairs collected at the Upsilon(4S) resonance with the BaBar detector. The analysis uses events in which the signal B decays are reconstructed with an innovative loose neutrino reconstruction technique. We obtain partial branching fractions in 12 bins of q2, the momentum transfer squared, from which we extract the f+(q2) form-factor shape and the total branching fraction BF(B0 --> pi l nu) = (1.46 +- 0.07(stat) +- 0.08(syst)) x 10^-4. Based on a recent unquenched lattice QCD calculation of the form factor in the range q2 > 16 GeV^2, we find the magnitude of the CKM matrix element |Vub| to be (4.1 +- 0.2(stat) +- 0.2(syst) +0.6-0.4(FF)) x 10^-3, where the last uncertainty is due to the normalization of the form factor.

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B. Aubert et al.. 2006-12-11. Measurement of the B0 --> pi l nu Form-Factor Shape and Branching Fraction, and Determination of |Vub| with a Loose Neutrino Reconstruction Technique. https://doi.org/10.1103/physrevlett.98.091801

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