Measurements of Branching Fractions and CP Asymmetries in Hadronic B Decays with η Meson in the Final State

We report measurements of two-body and three-body charmless hadronic B decays with at least one η meson in the final state. These results are obtained from a 140 fb^-1 data sample collected at Υ(4S) resonance with the Belle detector at the KEKB asymmetric energy e⁺e^- collider. In B to pseudoscalar-pseudoscalar (PP) decays, we have observed B⁺ → ηπ⁺ and B⁺ → K⁺ but no significant signals are found for neutral B meson decays. Significant signals are observed for the pseudoscalar-vector (PV) modes, B → ηK* and B⁺ → ηρ⁺ with branching fractions larger than the pseudoscalar-pseudoscalar modes. Flavor specific CP violating asymmetries for the observed decays are also reported. Large signals are observed for the inclusive three-body decays with measured branching fractions B(B⁰ -> ηK ^{+π ^-)} = ( 3 3.4_{3.3^{3.5(stat)_-1.9^+2.1(syst))}} × 10^-6 and B(B⁰ -> πK ^{+π ^-)} = (16.6_{-3.2^{3.5(stat)_-1.0^+1.4(syst))}} × 10^-6. Further study shows that the dominant contribution for B⁰ → ηK⁺π^- is the intermediate two-body states while in B⁰ → ηK⁺π^- the event topology is more phase-space like. We also search for the possible two-body decays, B^o -> a_0^{-K^+} and B^o -> a_{0^{-π ^+}}. No signals are observed and upper limits at 90% confidence level are provided.