Measurement of the B+ --> eta l+ nu and B+ --> eta' l+ nu Branching Fractions using Upsilon(4S)-->BBbar Events Tagged by a Fully Reconstructed B Meson

TL;DR

This paper reports preliminary measurements of specific B+ meson decay branching fractions involving eta and eta' mesons, using data from the BABAR detector at the Y(4S) resonance, providing new experimental limits.

Contribution

First measurement of B+ --> eta(') l+ nu branching fractions using fully reconstructed B mesons at BABAR.

Findings

Measured BR(B+ --> eta l+ nu) = (0.84 +/- 0.27 +/- 0.21) x 10^-4

Set upper limits BR(B+ --> eta l+ nu) < 1.4 x 10^-4 and BR(B+ --> eta' l+ nu) < 1.3 x 10^-4 at 90% CL

Utilized 316 fb^-1 of data at Y(4S) resonance with a novel tagging method.

Abstract

We report preliminary measurements of the exclusive charmless semileptonic branching fractions of the B+ --> eta l+ nu and B+ --> eta' l+ nu decays. These measurements are based on 316 fb-1 of data collected at the Y(4S) resonance by the BABAR detector. In events in which the decay of one B meson to a hadronic final state is fully reconstructed, the semileptonic decay of the recoiling B meson is identified by the detection of a charged lepton and an eta or eta'. We measure the branching fraction BR(B+ --> eta l+ nu) = (0.84 +/- 0.27 +/- 0.21) x 10-4, where the first error is statistical and the second one systematic. We also set an upper limit on the branching fraction of BR(B+ --> eta l+ nu) < 1.4 x 10-4 and BR(B+ --> eta' l+ nu) < 1.3 x 10^-4 at the 90% confidence level.