Measurement of the $B^{+}\to \omega l^{+}\nu$ and $B^{+}\to \eta l^{+}\nu$ branching fractions

We present a study of the charmless semileptonic $B$-meson decays $B^{+}\to \omega {\ell }^{+}\nu$ and $B^{+}\to \eta {\ell }^{+}\nu$. The analysis is based on $3.83\times {10}^8$ $B\overline{B}$ pairs recorded at the ${\rm Y}(4S)$ resonance with the BABAR detector. The $\omega$ mesons are reconstructed in the channel $\omega \to {\pi }^{+}{\pi }^{-}{\pi }^0$ and the $\eta$ mesons in the channels $\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0$ and $\eta \to \gamma \gamma$. We measure the branching fractions $\mathcal{B}(B^{+}\to \omega {\ell }^{+}\nu )=(1.14\pm {0.16}_{\mathrm{stat}}\pm {0.08}_{\mathrm{syst}})\times {10}^{-4}$ and $\mathcal{B}(B^{+}\to \eta {\ell }^{+}\nu )=(0.31\pm {0.06}_{\mathrm{stat}}\pm {0.08}_{\mathrm{syst}})\times {10}^{-4}$.

Figure 1

Projected $\Delta E$ distributions for $m_{\mathrm{ES}}>5.255\mathrm{GeV}$ (top), and $m_{\mathrm{ES}}$ distributions for $-0.2<\Delta E<0.4\mathrm{GeV}$ (bottom). From left to right: $B^{+}\to \omega {\ell }^{+}\nu$ channel, $B^{+}\to \eta {\ell }^{+}\nu$ channel with $\eta \to {\pi }^{+}{\pi }^{-}{\pi }^0$, $B^{+}\to \eta {\ell }^{+}\nu$ channel with $\eta \to \gamma \gamma$, and combined $B^{+}\to \eta {\ell }^{+}\nu$ channel. The error bars represent the statistical uncertainties on the data. The histograms show simulated distributions for signal (white), $B\to X_c\ell \nu$ decays (light shaded/yellow), $q\overline{q}$-continuum (dark shaded/blue), and all other backgrounds (hatched) and have been summed up. The distributions of the simulated signal and $B\to X_c\ell \nu$ background (and the $q\overline{q}$ background for $B^{+}\to \omega {\ell }^{+}\nu$) have been scaled to the results of the fits.