Measurement of the Branching Fractions for $B \to \omega K$ and $B \to \omega \pi$

Abstract

We report improved measurements of branching fractions for charmless hadronic two-body {\it B} meson decays containing an $\omega$ meson in the final state. The results are based on a data sample of 78 fb$^{-1}$ collected on the $\Upsilon(4S)$ resonance by the Belle detector. We measure the branching fractions ${\mathcal B}(B^+ \to \omega K^+) = (6.5^{+1.3}_{-1.2}\pm 0.6)\times 10^{-6}$ and ${\mathcal B}(B^+ \to \omega \pi^+) = (5.7^{+1.4}_{-1.3}\pm 0.6)\times 10^{-6}.$ We give 90% confidence upper limits for ${\mathcal B}(B^0 \to \omega K^0) < 7.6\times 10^{-6}$ and ${\mathcal B}(B^0 \to \omega \pi^0) < 1.9\times 10^{-6}.$ We also obtain the partial rate asymmetries ${\mathcal A}_{CP}=0.06^{+0.21}_{-0.18}\pm 0.01$ for $B^\pm \to \omega K^\pm$ and ${\mathcal A}_{CP}=0.50^{+0.23}_{-0.20}\pm 0.02$ for $B^\pm \to \omega \pi^\pm.$