Improved Measurements of Branching Fractions and CP Asymmetries in B-> eta h Decays

TL;DR

This paper presents improved measurements of B meson decays involving eta mesons, including branching fractions and CP asymmetries, using Belle detector data, with some decay modes observed and others constrained.

Contribution

First precise measurements of specific B->eta h decay modes, including branching fractions and CP asymmetries, with improved statistical and systematic uncertainties.

Findings

Observation of B+- -> eta pi+- and B+- -> eta K+- decays.

Measured branching fractions: (3.9 +- 0.5) x 10^-6 and (2.2 +- 0.4) x 10^-6.

CP asymmetries measured as -0.10 +- 0.11 and -0.55 +- 0.19.

Abstract

We report improved measurements of B decays with an eta meson in the final state using 357 fb^-1 of data collected by the Belle detector at the KEKB e^+ e^- collider. We observe the decays B^+- ->eta pi^+- and B^+- -> eta K^+-; the measured branching fractions are Br(B^+- -> eta pi^+-) = (3.9 +- 0.5(stat.)+-0.2(sys.))*10^-6 and Br(B^+- -> eta K^+-) = (2.2+-0.4(stat.)+-0.1(sys.))*10^-6, respectively. Their corresponding CP-violating asymmetries are measured to be -0.10+-0.11(stat.)+-0.02(sys.) for eta pi^+- and -0.55+-0.19(stat.)+0.04-0.03(sys.) for eta K^+-. No significant signal is found for B^0-> eta K^0 decays; the upper limit on the branching fraction at the 90% confidence level is Br(B^0->eta K^0) < 1.9*10^-6.