# Measurement of the B^0 --> pi^-ell^+nu and B^+ --> eta^(')ell^+nu Branching Fractions, the B^0 --> pi^-ell^+nu and B^+ --> eta ell^+nu Form-Factor Shapes, and Determination of |V_{ub}|

Abstract : We report the results of a study of the exclusive charmless semileptonic decays, $B^{+} \rightarrow \eta^{(\prime)} \ell^{+} \nu$ and $B^{0} \rightarrow \pi^{-} \ell^{+} \nu$, undertaken with approximately 464 million $\ensuremath{B\kern 0.18em\bar{\kern -0.18em B}}$ pairs collected at the $\Upsilon(4S)$ resonance with the ${{\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}}}$ detector. The analysis uses events in which the signal $B$ decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions for $B^{+} \rightarrow \eta \ell^{+} \nu$ and $B^{0} \rightarrow \pi^{-} \ell^{+} \nu$ decays in three and twelve bins of $q^2$, respectively, from which we extract the $f_+(q^2)$ form-factor shapes and the total branching fractions ${\ensuremath{\cal B}}(B^{+} \rightarrow \eta \ell^{+} \nu)$ $= \left(0.36 \pm 0.05_{stat} \pm 0.04_{syst} \right) \times 10^{-4}$ and ${\ensuremath{\cal B}}(B^{0} \rightarrow \pi^- \ell^{+} \nu)$ $= \left(1.42 \pm 0.05_{stat} \pm 0.08_{syst} \right) \times 10^{-4}$. We also measure ${\ensuremath{\cal B}}(B^{+} \rightarrow \eta^{\prime} \ell^{+} \nu)$ $= \left(0.24 \pm 0.08_{stat} \pm 0.03_{syst} \right) \times 10^{-4}$. We obtain values for the magnitude of the CKM matrix element $\ensuremath{|V_{ub}|}$ using three different QCD calculations.
Document type :
Journal articles

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Submitted on : Tuesday, October 26, 2010 - 10:28:28 AM
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### Citation

P. del Amo Sanchez, J.P. Lees, V. Poireau, E. Prencipe, V. Tisserand, et al.. Measurement of the B^0 --> pi^-ell^+nu and B^+ --> eta^(')ell^+nu Branching Fractions, the B^0 --> pi^-ell^+nu and B^+ --> eta ell^+nu Form-Factor Shapes, and Determination of |V_{ub}|. Physical Review D, American Physical Society, 2011, 83, pp.052011. ⟨10.1103/PhysRevD.83.052011⟩. ⟨in2p3-00529617⟩

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