Measurement of branching fractions and CP violation parameters in B →ωK decays with first evidence of CP violation in B0 →ω Ks0

Abstract

We present a measurement of the branching fractions and charge-parity-(CP-)violating parameters in B→ωK decays. The results are obtained from the final data sample containing 772×106 BB̄ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We obtain the branching fractions B(B0→ωK0)=(4.5±0.4(stat)±0.3(syst))×10-6, B(B+→ωK+)=(6.8±0.4(stat)±0.4(syst))×10-6 which are in agreement with their respective current world averages. For the CP-violating parameters, we obtain AωKS0=-0.36±0.19(stat)±0. 05(syst),SωKS0=+0.91±0.32(stat)±0.05(syst),AωK+=-0. 03±0.04(stat)±0.01(syst), where A and S represent the direct and mixing-induced CP asymmetry, respectively. We find no evidence of CP violation in the decay channel B+→ωK+; however, we obtain the first evidence of CP violation in the B0→ωKS0 decay channel at the level of 3.1 standard deviations. © 2014 American Physical Society.