Measurement of branching-fraction ratios and CP asymmetries in B^± → D_CP±K^± decays at Belle and Belle II

2023/08/09 by Belle, The, Collaborations, Belle II, : +427
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex)

paper · doi:10.48550/arxiv.2308.05048

Abstract

We report results from a study of B^± → DK^± decays followed by D decaying to CP~eigenstates, where D indicates a D⁰ or D⁰ meson. These decays are sensitive to the Cabibbo-Kobayashi-Maskawa unitarity-triangle angle ϕ₃. The results are based on a combined analysis of the final data set of 772 × 10⁶~BB pairs collected by the Belle experiment and a data set of 198 × 10⁶~BB pairs collected by the Belle~II experiment, both in electron-positron collisions at the Υ(4S) resonance. We measure the CP asymmetries to be A_{CP +} =~(+12.5 ± 5.8 ± 1.4)% and A_{CP -} =~(-16.7 ± 5.7 ± 0.6)%, and the ratios of branching fractions to be R_CP+=~1.164 ± 0.081 ± 0.036 and R_CP- =~1.151 ± 0.074 ± 0.019. The first contribution to the uncertainties is statistical, and the second is systematic. The asymmetries A_{CP +} and A_{CP -} have similar magnitudes and opposite signs; their difference corresponds to 3.5~standard deviations. From these values we calculate 68.3% confidence intervals of (8.5^∘<ϕ₃<16.5^∘) or (84.5^∘<ϕ₃<95.5^∘) or (163.3^∘<ϕ₃<171.5^∘) and 0.321

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