Observation of B^+ Meson Decays to a1(1260)^+ K^0 and B^0 to a1(1260)^- K^+

TL;DR

This paper reports measurements of branching fractions and charge asymmetries for B meson decays involving the a1(1260) resonance, using a large data sample from e+e- collisions at the Y(4S) resonance.

Contribution

It provides the first precise measurements of branching fractions and charge asymmetries for these specific B meson decay modes.

Findings

Measured branching fractions: (17.4 +/- 2.5 +/- 2.2) x 10^{-6} for B+ decays.

Measured branching fractions: (8.2 +/- 1.5 +/- 1.2) x 10^{-6} for B0 decays.

Charge asymmetries are consistent with zero within uncertainties.

Abstract

We present branching fraction measurements of the decays B^{+} -> a1(1260)^{+} K^{0} and B^{0} to a1(1260)^{-} K^{+} with a1(1260)^{+} -> pi^{-} pi^{+} pi^{+}. The data sample corresponds to 383 million B B-bar pairs produced in e^{+}e^{-} annihilation through the Y(4S) resonance. We measure the products of the branching fractions: B(B^{+}-> a1(1260)^{+} K^{0})B(a1(1260)^{+} -> pi^{-} pi^{+} pi^{+}) = (17.4 +/- 2.5 +/- 2.2) 10^{-6} B(B^{0}-> a1(1260)^{-} K^{+})B(a1(1260)^{-} -> pi^{+} pi^{-} pi^{-}) = (8.2 +/- 1.5 +/- 1.2) 10^{-6}. We also measure the charge asymmetries A_{ch}(B^{+} -> a1(1260)^{+} K^{0})= 0.12 +/- 0.11 +/- 0.02 and A_{ch}(B^{0} -> a1(1260)^{-} K^{+})= -0.16 +/- 0.12 +/- 0.01. The first uncertainty quoted is statistical and the second is systematic.