arXiv subjects

A. Budano

Publications and source records attributed to A. Budano.

At least 199 records · Page 11Linked to original sources

arXiv2022

Measurement of decay-time dependent $CP$ violation in $B^0 \rightarrow K^0_S K^0_S K^0_S$ using 2019--2021 Belle II data

We report a measurement of decay-time dependent $CP$-violating parameters in $B^0 \rightarrow K^0_S K^0_S K^0_S$ decays. We use $(198.0 \pm 3.0) \times 10^6\ B\overline{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle II detector at the SuperKEKB asymmetric-energy $e^+e^-$ collider. The observed mixing-induced and direct $CP$ violation parameters are $\mathcal{S} = -1.86\ _{-0.46}^{+0.91}~{\rm (stat)} \pm 0.09~{\rm (syst)}$ and $\mathcal{A} = -0.22\ _{-0.27}^{+0.30}~{\rm (stat)} \pm 0.04~{\rm (syst)}$, respectively.

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arXiv2022

Study of Exclusive $B \to πe^+ ν_e$ Decays with Hadronic Full-event-interpretation Tagging in 189.3 fb$^{-1}$ of Belle II Data

We present a reconstruction of the semileptonic decays $B^0 \to π^- e^+ ν_e$ and $B^+ \to π^0 e^+ ν_e$ in a sample corresponding to 189.3 fb$^{-1}$ of Belle II data, using events where the partner $B$-meson is reconstructed from a large variety of hadronic channels via a tagging algorithm known as the full-event-interpretation. We determine the partial branching fractions in three bins of the squared momentum transfer to the leptonic system using fits to the distribution of the square of the missing mass. The partial branching fractions are summed to determine $\mathcal{B}(B^0 \to π^- e^+ ν_e)$ = (1.43 $\pm$ 0.27(stat) $\pm$ 0.07(syst)) $\times 10^{-4}$ and $\mathcal{B}(B^+ \to π^0 e^+ ν_e)$ = (8.33 $\pm$ 1.67(stat) $\pm$ 0.55(syst)) $\times 10^{-5}$. We extract a first Belle II measurement of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{\mathrm{ub}}|$, with $|V_{\mathrm{ub}}|$ = (3.88 $\pm$ 0.45) $\times 10^{-3}$.

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arXiv2022

Measurement of the branching fraction for the decay $B \to K^{\ast}(892)\ell^+\ell^-$ at Belle II

We report a measurement of the branching fraction of $B \to K^{\ast}(892)\ell^+\ell^-$ decays, where $\ell^+\ell^- = μ^+μ^-$ or $e^+e^-$, using electron-positron collisions recorded at an energy at or near the $Υ(4S)$ mass and corresponding to an integrated luminosity of $189$ fb$^{-1}$. The data was collected during 2019--2021 by the Belle II experiment at the SuperKEKB $e^{+}e^{-}$ asymmetric-energy collider. We reconstruct $K^{\ast}(892)$ candidates in the $K^+π^-$, $K_{S}^{0}π^+$, and $K^+π^0$ final states. The signal yields with statistical uncertainties are $22\pm 6$, $18 \pm 6$, and $38 \pm 9$ for the decays $B \to K^{\ast}(892)μ^+μ^-$, $B \to K^{\ast}(892)e^+e^-$, and $B \to K^{\ast}(892)\ell^+\ell^-$, respectively. We measure the branching fractions of these decays for the entire range of the dilepton mass, excluding the very low mass region to suppress the $B \to K^{\ast}(892)γ(\to e^+e^-)$ background and regions compatible with decays of charmonium resonances, to be \begin{equation} {\cal B}(B \to K^{\ast}(892)μ^+μ^-) = (1.19 \pm 0.31 ^{+0.08}_{-0.07}) \times 10^{-6}, {\cal B}(B \to K^{\ast}(892)e^+e^-) = (1.42 \pm 0.48 \pm 0.09)\times 10^{-6}, {\cal B}(B \to K^{\ast}(892)\ell^+\ell^-) = (1.25 \pm 0.30 ^{+0.08}_{-0.07}) \times 10^{-6}, \end{equation} where the first and second uncertainties are statistical and systematic, respectively. These results, limited by sample size, are the first measurements of $B \to K^{\ast}(892)\ell^+\ell^-$ branching fractions from the Belle II experiment.

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arXiv2022

Measurement of the branching fractions and $CP$ asymmetries of $B^+ \rightarrow π^+ π^0$ and $B^+ \rightarrow K^+ π^0$ decays in 2019-2021 Belle II data

We determine the branching fractions ${\mathcal{B}}$ and $CP$ asymmetries ${\mathcal{A}_{\it CP}}$ of the decays $B^+ \rightarrow π^+ π^0$ and $B^+ \rightarrow K^+ π^0$. The results are based on a data set containing 198 million bottom-antibottom meson pairs corresponding to an integrated luminosity of $190\;\text{fb}^{-1}$ recorded by the Belle II detector in energy-asymmetric electron-positron collisions at the $Υ(4S)$ resonance. We measure ${\mathcal{B}(B^+ \rightarrow π^+ π^0) = (6.12 \pm 0.53 \pm 0.53)\times 10^{-6}}$, ${\mathcal{B}(B^+ \rightarrow K^+ π^0) = (14.30 \pm 0.69 \pm 0.79)\times 10^{-6}}$, ${\mathcal{A}_{\it CP}(B^+ \rightarrow π^+ π^0) = -0.085 \pm 0.085 \pm 0.019}$, and ${\mathcal{A}_{\it CP}(B^+ \rightarrow K^+ π^0) = 0.014 \pm 0.047 \pm 0.010}$, where the first uncertainties are statistical and the second are systematic. These results improve a previous Belle II measurement and agree with the world averages.

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arXiv2022

Measurement of Branching Fraction and Longitudinal Polarization in $B^0 \to ρ^+ ρ^-$ Decays at Belle II

We present a measurement of the branching fraction and longitudinal polarization of $B^0 \to ρ^+ ρ^-$ decays. SuperKEKB electron-positron collision data corresponding to 189~fb$^{-1}$ of integrated luminosity and containing $198 \times 10^6 B\bar{B}$ pairs collected with the Belle II detector are used. We obtain \begin{eqnarray*} \mathcal{B}(B^0\toρ^+ρ^-) &=& [2.67\pm0.28\,(\mathrm{stat})\,\pm0.28\,(\mathrm{syst})] \times 10^{-5}, \end{eqnarray*} \begin{eqnarray*} f_L &=& 0.956\pm0.035\,(\mathrm{stat})\,\pm 0.033\,(\mathrm{syst}), \end{eqnarray*} These results are consistent with previous measurements and can be used to constrain penguin pollution and to extract the quark-mixing angle $ϕ_2$.

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arXiv2022

Measurements of the branching fraction, isospin asymmetry, and lepton-universality ratio in $B \to J/ψK$ decays at Belle II

We report a study of $B \to J/ψ(\ell^{+}\ell^{-})K$ decays, where $\ell$ represents an electron or a muon, using $e^{+}e^{-}$ collisions at the $Υ(4S)$ resonance. The data were collected by the Belle II experiment at the SuperKEKB asymmetric-energy collider during 2019-2021, corresponding to an integrated luminosity of $189$ fb$^{-1}$. The measured quantities are the branching fractions (${\mathcal B}$) of the decay channels $B^{+} \to J/ψ(e^{+}e^{-})K^{+}$, $B^{+} \to J/ψ(μ^{+}μ^{-}) K^{+}$, $B^{0} \to J/ψ(e^{+}e^{-}) K^{0}_{S}$, and $B^{0} \to J/ψ(μ^{+}μ^{-})K^{0}_{S}$; the lepton-flavor-dependent isospin asymmetries for the electron [$A_{I}\left(B \to J/ψ(e^{+}e^{-}) K\right)$] and muon [$A_{I}\left(B \to J/ψ(μ^{+} μ^{-}) K\right)$] channels; and the ratios of branching fractions between the muon and electron channels for the charged [$R_{K^{+}}\left(J/ψ\right)$] and neutral kaon [$R_{K^{0}}\left(J/ψ\right)$] case. The measurements are consistent with the world-average values.

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arXiv2022

Angular analysis of $B^+ \to ρ^+ρ^0$ decays reconstructed in 2019, 2020, and 2021 Belle II data

We report on a Belle II measurement of the branching fraction ($\mathcal{B}$), longitudinal polarization fraction ($f_L$), and CP asymmetry ($\mathcal{A}_{CP}$) of $B^+\to ρ^+ρ^0$ decays. We reconstruct $B^+\to ρ^+(\to π^+π^0(\to γγ))ρ^0(\to π^+π^-)$ decays in a sample of SuperKEKB electron-positron collisions collected by the Belle II experiment in 2019, 2020, and 2021 at the $Υ$(4S) resonance and corresponding to 190 fb$^{-1}$ of integrated luminosity. We fit the distributions of the difference between expected and observed $B$ candidate energy, continuum-suppression discriminant, dipion masses, and decay angles of the selected samples, to determine a signal yield of $345 \pm 31$ events. The signal yields are corrected for efficiencies determined from simulation and control data samples to obtain $\mathcal{B}(B^+ \to ρ^+ρ^0) = [23.2^{+\ 2.2}_{-\ 2.1} (\rm stat) \pm 2.7 (\rm syst)]\times 10^{-6}$, $f_L = 0.943 ^{+\ 0.035}_{-\ 0.033} (\rm stat)\pm 0.027(\rm syst)$, and $\mathcal{A}_{CP}=-0.069 \pm 0.068(\rm stat) \pm 0.060 (\rm syst)$. The results agree with previous measurements. This is the first measurement of $\mathcal{A}_{CP}$ in $B^+\to ρ^+ρ^0$ decays reported by Belle II.

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arXiv2022

Measurement of the branching fraction of the $B^0 \to K_S^0 π^0 γ$ decay using 190 fb$^{-1}$ of Belle II data

We report the measurement of the branching fraction of the $B^0 \to K_S^0 π^0 γ$ decay in $e^+ e^- \to Υ(4S) \to B \overline{B}$ data recorded by the Belle II experiment at the SuperKEKB asymmetric-energy collider and corresponding to 190 fb$^{-1}$ of integrated luminosity. The signal yield is measured to be $121\pm 29\,\hbox{(stat.)}$, leading to the branching fraction ${\cal B}\left(B^0 \to K_S^0 π^0 γ\right) = \left(7.3 \pm 1.8\,\hbox{(stat.)} \pm 1.0\,\hbox{(syst.)} \right)\times 10^{-6}$, which agrees with the known value.

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arXiv2022

First decay-time-dependent analysis of $B^{0} \to K_{S}^{0} π^{0}$ at Belle II

We report measurements of the branching fraction ($\mathcal{B}$) and direct $CP$-violating asymmetry ($A_{CP}$) of the charmless decay $B^{0} \to K^0 π^0$ at Belle II. A sample of $e^{+} e^{-}$ collisions, corresponding to $189.8 fb^{-1}$ of integrated luminosity, recorded at the $Υ(4S)$ resonance is used for the first decay-time-dependent analysis of these decays within the experiment. We reconstruct about 135 signal candidates, and measure $\mathcal{B}(B^{0} \to K^{0} π^{0})= [11.0 \pm 1.2 (stat) \pm 1.0 (syst)] \times 10^{-6}$ and $A_{CP} (B^{0} \to K^{0} π^{0})= -0.41_{-0.32}^{+0.30} (stat) \pm 0.09 (syst)$.

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arXiv2022

First test of Lepton Flavor Universality in the charmed baryon decays $Ω^{0}_{c} \to Ω^{-} \ell^{+} ν_{\ell}$ using data of the Belle experiment

We present the first observation of the $Ω_{c}^{0} \to Ω^{-} μ^{+} ν_μ$ decay and present measurements of the branching fraction ratios of the $Ω_{c}^{0} \to Ω^{-} \ell^{+} ν_{\ell}$ decays compared to the reference mode $Ω_{c}^{0} \to Ω^{-} π^+$, ($\ell = e$ or $μ$). This analysis is based on 89.5 fb$^{-1}$, 711 fb$^{-1}$, and 121.1 fb$^{-1}$ data samples collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider at the center-of-mass energies of 10.52 GeV, 10.58 GeV, and 10.86 GeV, respectively. The $Ω_{c}^{0}$ signal yields are extracted by fitting $M_{Ω^{-} \ell^{+}}$ and $M_{Ω^{-}π^+}$ spectra. The branching fraction ratios ${\cal B}(Ω_{c}^{0} \to Ω^{-} e^{+} ν_{e})/{\cal B}(Ω_{c}^{0} \to Ω^{-} π^+)$ and ${\cal B}(Ω_{c}^{0} \to Ω^{-} μ^{+} ν_μ)/{\cal B}(Ω_{c}^{0} \to Ω^{-} π^+)$ are measured to be $1.98 \pm0.13~({\rm stat.}) \pm 0.08~({\rm syst.})$ and $ 1.94 \pm 0.18~({\rm stat.}) \pm 0.10~({\rm syst.})$, respectively. The ratio of ${\cal B}(Ω_{c}^{0} \to Ω^{-} e^{+} ν_{e})/{\cal B}(Ω_{c}^{0} \to Ω^{-} μ^{+} ν_μ)$ is measured to be $1.02 \pm 0.10~({\rm stat.}) \pm 0.02~({\rm syst.})$, which is consistent with the expectation of lepton flavor universality.

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arXiv2022

Search for charged lepton flavor violating decays of $Υ(1S)$

We present a search for the charged lepton-flavor-violating decays $Υ(1S)\rightarrow\ell\ell^\prime$ and radiative charged lepton-flavour-violating decays $Υ(1S)\rightarrowγ\ell\ell^\prime$ [$\ell,\ell^\prime = e, μ, τ$] using the 158 million $Υ(2S)$ sample collected by the Belle detector at the KEKB collider. This search uses $Υ(1S)$ mesons produced in $π^+π^-Υ(1S)$ transitions. We do not find any significant signal, so we provide upper limits on the branching fractions at the 90% confidence level.

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arXiv2022

Precision tests of Quantum Mechanics and CPT symmetry with entangled neutral kaons at KLOE

The quantum interference between the decays of entangled neutral kaons is studied in the process $ϕ\rightarrow K_S K_L \rightarrowπ^+π^-π^+π^-$, which exhibits the characteristic Einstein--Podolsky--Rosen correlations that prevent both kaons to decay into $π^+π^-$ at the same time. This constitutes a very powerful tool for testing at the utmost precision the quantum coherence of the entangled kaon pair state, and to search for tiny decoherence and CPT violation effects, which may be justified in a quantum gravity framework. The analysed data sample was collected with the KLOE detector at DA$Φ$NE, the Frascati $ϕ$-factory, and corresponds to an integrated luminosity of about 1.7 fb$^{-1}$, i.e. to about $1.7 \times 10^9$ $ϕ\rightarrow K_S K_L$ decays produced. From the fit of the observed $Δt$ distribution, being $Δt$ the difference of the kaon decay times, the decoherence and CPT violation parameters of various phenomenological models are measured with a largely improved accuracy with respect to previous analyses. The results are consistent with no deviation from quantum mechanics and CPT symmetry, while for some parameters the precision reaches the interesting level at which -- in the most optimistic scenarios -- quantum gravity effects might show up. They provide the most stringent limits up to date on the considered models.

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arXiv2022

$B$-flavor tagging at Belle II

We report on new flavor tagging algorithms developed to determine the quark-flavor content of bottom ($B$) mesons at Belle II. The algorithms provide essential inputs for measurements of quark-flavor mixing and charge-parity violation. We validate and evaluate the performance of the algorithms using hadronic $B$ decays with flavor-specific final states reconstructed in a data set corresponding to an integrated luminosity of $62.8$ fb$^{-1}$, collected at the $Υ$(4$S$) resonance with the Belle II detector at the SuperKEKB collider. We measure the total effective tagging efficiency to be $\varepsilon_{\rm eff} = \big(30.0 \pm 1.2(\text{stat}) \pm 0.4(\text{syst})\big)\%$ for a category-based algorithm and $\varepsilon_{\rm eff} = \big(28.8 \pm 1.2(\text{stat}) \pm 0.4(\text{syst})\big)\%$ for a deep-learning-based algorithm.

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arXiv2022

Search for $B^{0} \to K_S^{0}K_S^{0}γ$ decays at Belle

We report the first search for the penguin-dominated process $B^0 \rightarrow K_S^0 K_S^0 γ$ using the full data sample of $772\times 10^6$ $B\bar{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We do not observe any statistically significant signal yield in the $K_S^0$-pair invariant mass range 1 GeV/$c^2 < M_{K_S^0 K_S^0} < $ 3 GeV/$c^2$, and set the following upper limits at 90% confidence level: $\mathcal{B}(B^0 \to K_S^0 K_S^0 γ) < 5.8\times10^{-7}$, $\mathcal{B}(B^0 \to f_2 γ)\times \mathcal{B}(f_2 (1270) \to K_S^0 K_S^0 ) < 3.1\times10^{-7}$, and $\mathcal{B}(B^0 \to f_2^{\prime} γ)\times \mathcal{B}(f_2^{\prime} (1525) \to K_S^0 K_S^0 ) < 2.1\times10^{-7}$. Further, 90% confidence upper limits have also been set in the range of [0.7-2.9]$\times10^{-7}$ on the $B^0 \rightarrow K_S^0 K_S^0 γ$ branching fraction in bins of $M_{K_S^0 K_S^0}$.

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arXiv2022

First Measurement of the $Λ_c^+ \to p η'$ decay

We present the first measurement of the branching fraction of the singly Cabibbo-suppressed (SCS) decay $Λ_c^+ \to p η'$ with $η' \to ηπ^+π^-$, using a data sample corresponding to an integrated luminosity of 981 $\rm fb^{-1}$, collected by the Belle detector at the KEKB $e^{+}$$e^{-}$ asymmetric-energy collider. A significant $Λ_c^+$ signal is observed for the first time with a signal significance of 5.4$σ$. The relative branching fraction with respect to the normalization mode $Λ_c^+ \to pK^-π^+$ is measured to be \begin{equation*} \frac{{\cal B}(Λ_c^+ \to p η')}{{\cal B}(Λ_c^+ \to p K^-π^+)} = (7.54 \pm 1.32 \pm 0.75) \times 10^{-3}, \end{equation*} where the uncertainties are statistical and systematic, respectively. Using the world-average value of ${\cal B}(Λ_c^+ \to p K^-π^+) = (6.28\pm0.32)\times10^{-2}$, we obtain \begin{equation*} {\cal B}(Λ_c^+ \to p η') = (4.73 \pm 0.82 \pm 0.47 \pm 0.24)\times 10^{-4}, \end{equation*} where the uncertainties are statistical, systematic, and from ${\cal B}(Λ_c^+ \to pK^-π^+)$, respectively.

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arXiv2022

Search for a light Higgs boson in single-photon decays of $Υ(1S)$ using $Υ(2S) \to π^+ π^- Υ(1S)$ tagging method

We search for a light Higgs boson ($A^0$) decaying into a $τ^+τ^-$ or $μ^+μ^-$ pair in the radiative decays of $Υ(1S)$. The production of $Υ(1S)$ mesons is tagged by $Υ(2S)\to π^+ π^- Υ(1S)$ transitions, using 158 million $Υ(2S)$ events accumulated with the Belle detector at the KEKB asymmetric energy electron-positron collider. No significant $A^0$ signals in the mass range from the $τ^+τ^-$ or $μ^+μ^-$ threshold to 9.2 GeV/$c^2$ are observed. We set the upper limits at 90\% credibility level (C.L.) on the product branching fractions for $Υ(1S)\to γA^0$ and $A^0\to τ^+τ^-$ varying from $3.8\times10^{-6}$ to $1.5\times10^{-4}$. Our results represent an approximately twofold improvement on the current world best upper limits for the $Υ(1S)\to γA^0(\to τ^+τ^-)$ production. For $A^0\to μ^+μ^-$, the upper limits on the product branching fractions for $Υ(1S)\to γA^0$ and $A^0\to μ^+μ^-$ are at the same level as the world average limits, and vary from $3.1\times10^{-7}$ to $1.6\times10^{-5}$. The upper limits at 90\% C.L. on the Yukawa coupling $f_{Υ(1S)}$ and mixing angle ${\rm sin}θ_{A^0}$ are also given.

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arXiv2022

Search for tetraquark states $X_{cc\bar{s}\bar{s}}$ in $D_{s}^{+}D_{s}^{+}~(D_{s}^{+}D_{s}^{+})$ final states at Belle

A search for double-heavy tetraquark state candidates $X_{cc\bar{s}\bar{s}}$ decaying to $D_{s}^{+}D_{s}^{+}$ and $D_{s}^{*+} D_{s}^{*+}$ is presented for the first time using the data samples of 102 million $Υ(1S)$ and 158 million $Υ(2S)$ events, and the data samples at $\sqrt{s}$ = 10.52~GeV, 10.58~GeV, and 10.867~GeV corresponding to integrated luminosities of 89.5~fb$^{-1}$, 711.0~fb$^{-1}$, and 121.4~fb$^{-1}$, respectively, accumulated with the Belle detector at the KEKB asymmetric energy electron-positron collider. The invariant-mass spectra of the $D_{s}^{+}D_{s}^{+}$ and $D_{s}^{*+} D_{s}^{*+}$ are studied to search for possible resonances. No significant signals are observed, and the 90\% confidence level upper limits on the product branching fractions [${\cal B}(Υ(1S,2S) \to X_{cc\bar{s}\bar{s}} + anything) \times {\cal B}(X_{cc\bar{s}\bar{s}} \to D_{s}^{+}D_{s}^{+}(D_{s}^{*+} D_{s}^{*+}))$] in $Υ(1S,2S)$ inclusive decays and the product values of Born cross section and branching fraction [$σ(e^+e^- \to X_{cc\bar{s}\bar{s}} + anything ) \times {\cal B}(X_{cc\bar{s}\bar{s}} \to D_{s}^{+}D_{s}^{+}(D_{s}^{*+} D_{s}^{*+}))$] in $e^+e^-$ collisions at $\sqrt{s}$ = 10.52~GeV, 10.58~GeV, and 10.867~GeV under different assumptions of $X_{cc\bar{s}\bar{s}}$ masses and widths are obtained.

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arXiv2022

Study of $\overline{B}{}^0\rightarrow D^{+}h^{-} (h=K/π)$ decays at Belle

We present a measurement of the branching fractions of the Cabibbo favored $\overline{B}{}^0\rightarrow D^{+}π^{-}$ and the Cabibbo suppressed $\overline{B}{}^0\rightarrow D^{+}K^{-}$ decays. We find $\mathcal{B}(\overline{B}{}^0\rightarrow D^{+}π^{-}) = (2.48 \pm 0.01 \pm 0.09 \pm 0.04) \times 10^{-3}$ and $\mathcal{B}(\overline{B}{}^0\rightarrow D^{+}K^{-})= (2.03 \pm 0.05 \pm 0.07 \pm 0.03) \times 10^{-4}$ decays, where the first uncertainty is statistical, the second is systematic, and the third uncertainty is due to the $D^{+} \rightarrow K^{-}π^{+}π^{+}$ branching fraction. The ratio of branching fractions of $\overline{B}{}^0\rightarrow D^{+}K^{-}$ and $\overline{B}{}^0\rightarrow D^{+}π^{-}$ is measured to be $R^{D} = [8.19 \pm 0.20(\rm stat) \pm 0.23(\rm syst)] \times 10^{-2} $. These measurements are performed using the full Belle data set, which corresponds to $772 \times 10^{6} B\overline{B} $ pairs.

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