Measurement of the decays B → ηlνl and B → η'lνl in fully reconstructed events at Belle

Le résumé fourni par la source

We report branching fraction measurements of the decays B þ → ηl þ ν l and B þ → η 0 l þ ν l based on 711 fb -1 of data collected near the ϒð4SÞ resonance with the Belle experiment at the KEKB asymmetricenergy e þ e -collider.This data sample contains 772 million B B events.One of the two B mesons is fully reconstructed in a hadronic decay mode.Among the remaining ("signal-B") daughters, we search for the η meson in two decay channels, η → γγ and η → π þ π -π 0 , and reconstruct the η 0 meson in η 0 → ηπ þ π -with subsequent decay of the η into γγ.Combining the two η modes and using an extended maximum likelihood, the B þ → ηl þ ν l branching fraction is measured to be ð4.2Æ 1.1ðstat:Þ Æ 0.3ðsyst:ÞÞ × 10 -5 .For B þ → η 0 l þ ν l , we observe no significant signal and set an upper limit of 0.72 × 10 -4 at 90% confidence level.

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