MEASUREMENTS OF BRANCHING FRACTIONS AND CP ASYMMETRIES IN HADRONIC B DECAYS WITH η MESON IN THE FINAL STATE

摘要

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(B~0 → ηK~+π~-) = (33.4_(-3.3)~(+3.5)(stat)_(-1.9)~(+2.1)(ayst)) x 10~(-6) and B(B~0 → ηπ~+π~-) = (16.6_(-3.2)~(+3.5)(stat)_(-1.0)~(+1.4)(syst)) x 10~(-6). Further study shows that the dominant contribution for B~0 → ηK~+π~- is the intermediate two-body states while in B~0 → ηK~+π~- the event topology is more phase-space like. We also search for the possible two-body decays, B~0 → a_0~- K~+ and B~0 → a_0~-π~+. No signals are observed and upper limits at 90% confidence level are provided.