Measurement of Branching Fractions and 𝐶𝑃 Violation Parameters in 𝐵 →𝜔𝐾 Decays With First Evidence of 𝐶𝑃 Violation in 𝐵⁰ →𝜔𝐾ₛ⁰

Abstract

[Abstract] We present a measurement of the branching fractions and charge-parity-(𝐶⁢𝑃-)violating parameters in 𝐵 → 𝜔⁢𝐾 decays. The results are obtained from the final data sample containing 772×106 𝐵⁢𝐵 pairs collected at the Υ⁡(4⁢𝑆) resonance with the Belle detector at the KEKB asymmetric-energy 𝑒+⁢𝑒− collider. We obtain the branching fractions ℬ⁡(𝐵0 → 𝜔⁢𝐾0) = (4.5 ± 0.4⁢(stat) ± 0.3⁢(syst)) × 10−6,ℬ⁡(𝐵+ → 𝜔⁢𝐾+) = (6.8 ± 0.4⁢(stat) ± 0.4⁢(syst)) × 10−6 which are in agreement with their respective current world averages. For the 𝐶⁢𝑃-violating parameters, we obtain 𝒜𝜔⁢𝐾0𝑆 = −0.36 ± 0.19⁢(stat) ± 0.05⁢(syst), 𝒮𝜔⁢𝐾0𝑆 = +0.91 ± 0.32⁢(stat) ± 0.05⁢(syst),𝒜𝜔⁢𝐾+ = −0.03 ± 0.04⁢(stat) ± 0.01⁢(syst), where 𝒜 and 𝒮 represent the direct and mixing-induced 𝐶⁢𝑃 asymmetry, respectively. We find no evidence of 𝐶⁢𝑃 violation in the decay channel 𝐵+ → 𝜔⁢𝐾+; however, we obtain the first evidence of 𝐶⁢𝑃 violation in the 𝐵0 → 𝜔⁢𝐾0𝑆 decay channel at the level of 3.1 standard deviations.