Study of B --> pi l nu and B --> rho l nu Decays and Determination of |V_ub|

Abstract

We present an analysis of exclusive charmless semileptonic B-meson decays based on 377 million BBbar pairs recorded with the BABAR detector at the Upsilon(4S) resonance. We select four event samples corresponding to the decay modes B0 --> pi- l+ nu, B+ --> pi0 l+ nu, B0 --> rho- l+ nu, and B+ -> rho0 l+ nu, and find the measured branching fractions to be consistent with isospin symmetry. Assuming isospin symmetry, we combine the two B --> pi l nu samples, and similarly the two B --> rho l nu samples, and measure the branching fractions BF(B0 --> pi- l+ nu) = (1.41 +- 0.05 +- 0.07) x 10^-4 and BF(B0 --> rho- l+ nu) = (1.75 +- 0.15 +- 0.27) x 10^-4, where the errors are statistical and systematic. We compare the measured distribution in q^2, the momentum transfer squared, with predictions for the form factors from QCD calculations and determine the CKM matrix element |V_ub|. Based on the measured partial branching fraction for B --> pi l nu in the range q^2 < 12 GeV^2 and the most recent LCSR calculations we obtain |V_ub| = (3.78 +- 0.13 +0.55-0.40) x 10^-3, where the errors refer to the experimental and theoretical uncertainties. From a simultaneous fit to the data over the full q^2 range and the FNAL/MILC lattice QCD results, we obtain |V_ub| = (2.95 +- 0.31) x 10^-3 from B --> pi l nu, where the error is the combined experimental and theoretical uncertainty.

47 pages, 26 postscript figures, accepted by Phys. Rev. D

References in corpus (4)

• The B -> pi l nu semileptonic form factor from three-flavor lattice QCD: A model-independent determination of |V(ub)|
• Observation of Time-Dependent CP Violation in B0 -> eta' K0 Decays and Improved Measurements of CP Asymmetries in B0 -> phiK0, KsKsKs and B0 -> J/psi K0 Decays
• |V_ub| from UTangles and B->pi l nu
• The Kl3 scalar form factors in the standard model

Cited by in corpus (5)

• $B\to \pi \ell {\nu }_l$ Width and $|V_{ub}|$ from QCD Light-Cone Sum Rules
• Determination of the strong coupling $g_{B^{\ast }B\pi }$ from semi-leptonic $B\to \pi \ell \nu$ decay
• Constraints on B--->pi,K transition form factors from exclusive semileptonic D-meson decays
• CP violation and CKM matrix elements at the B factories
• CKM angles and sides from BaBar