Measurement of branching-fraction ratios and $CP$ asymmetries in $B^{pm} to D_{CPpm}K^{pm}$ decays at Belle and Belle II

Kavli Affiliate: T. Higuchi

| First 5 Authors: The Belle, Belle II Collaborations, :, I. Adachi, L. Aggarwal

| Summary:

We report results from a study of $B^pm rightarrow DK^pm$ decays followed
by $D$ decaying to $CP$~eigenstates, where $D$ indicates a $D^0$ or
$bar{D}^{0}$ meson. These decays are sensitive to the
Cabibbo-Kobayashi-Maskawa unitarity-triangle angle $phi_{3}$. The results are
based on a combined analysis of the final data set of $772 times
10^6~Bbar{B}$ pairs collected by the Belle experiment and a data set of $198
times 10^6~Bbar{B}$ pairs collected by the Belle~II experiment, both in
electron-positron collisions at the $Upsilon(4S)$ resonance. We measure the
$CP$ asymmetries to be $mathcal{ A}_{CP +} =~(+12.5 pm 5.8 pm 1.4)% $ and
$mathcal{ A}_{CP -} =~(-16.7 pm 5.7 pm 0.6)%$, and the ratios of branching
fractions to be $mathcal{ R}_{CP+}=~1.164 pm 0.081 pm 0.036 $ and $mathcal{
R}_{CP-} =~1.151 pm 0.074 pm 0.019$. The first contribution to the
uncertainties is statistical, and the second is systematic. The asymmetries
$mathcal{A}_{CP +}$ and $mathcal{A}_{CP -}$ have similar magnitudes and
opposite signs; their difference corresponds to 3.5~standard deviations. From
these values we calculate 68.3% confidence intervals of
($8.5^{circ}<phi_{3}<16.5^{circ}$) or ($84.5^{circ}<phi_{3}<95.5^{circ}$)
or ($163.3^{circ}<phi_{3}<171.5^{circ}$) and $0.321<r_{B}<0.465$.

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