# A search for B^+ -> l^+ nu_l recoiling against B^- -> D^0 l^- nu X

Abstract : We present a search for the decay $B^+ \to \ell^+ \nu_{\ell}$ ($\ell = e,\mu\tau$) in $(458.9 \pm 5.1) \times 10^6$ $B\bar{B}$ pairs recorded with the BABAR detector at the PEP-II B-Factory. We search for these B decays in a sample of $B^+B^-$ events where one $B$-meson is reconstructed as $B^- \to D^0 \ell^- \nu X$. Using the method of Feldman and Cousins, we obtain $\mathcal{B}(B^+ \to \tau^+ \nu) = (1.7 \pm 0.8 \pm 0.2) \times 10^{-4}$, which excludes zero at $2.3\sigma$. We interpret the central value in the context of the Standard Model and find the B meson decay constant to be $f^2_B = (62 \pm 31) \times 10^3 \mathrm{MeV}^2$. We find no evidence for $B^+ \to e^+ \nu_{e}$ and $B^+ \to \mu^+ \nu_{\mu}$ and set upper limits at the 90% C.L. $\mathcal{B}(B^+ \to e^+ \nu_{e}) < 0.8 \times 10^{-5}$ and $\mathcal{B}(B^+ \to \mu^+ \nu_{\mu}) < 1.1 \times 10^{-5}$.
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http://hal.in2p3.fr/in2p3-00441222
Contributor : Swarna Bassava <>
Submitted on : Tuesday, December 15, 2009 - 11:03:20 AM
Last modification on : Tuesday, December 22, 2020 - 12:40:02 PM

### Citation

B. Aubert, Y. Karyotakis, J. P. Lees, V. Poireau, E. Prencipe, et al.. A search for B^+ -> l^+ nu_l recoiling against B^- -> D^0 l^- nu X. Physical Review D, American Physical Society, 2010, 81, pp.051101. ⟨10.1103/PhysRevD.81.051101⟩. ⟨in2p3-00441222⟩

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