arXiv subjects

S. Jia

Publications and source records attributed to S. Jia.

At least 73 records · Page 4Linked to original sources

arXiv2023

Measurement of Differential Distributions of $B \to D^* \ell \bar ν_\ell$ and Implications on $|V_{cb}|$

We present a measurement of the differential shapes of exclusive $B\to D^* \ell \barν_\ell$ ($B = B^-, \bar{B}^0 $ and $\ell = e, μ$) decays with hadronic tag-side reconstruction for the full Belle data set of $711\,\mathrm{fb}^{-1}$ integrated luminosity. We extract the Caprini-Lellouch-Neubert (CLN) and Boyd-Grinstein-Lebed (BGL) form factor parameters and use an external input for the absolute branching fractions to determine the Cabibbo-Kobayashi-Maskawa matrix element and find $|V_{cb}|_\mathrm{CLN} = (40.1\pm0.9)\times 10^{-3}$ and $|V_{cb}|_\mathrm{BGL} = (40.6\pm 0.9)\times 10^{-3}$ with the zero-recoil lattice QCD point $\mathcal{F}(1) = 0.906 \pm 0.013$. We also perform a study of the impact of preliminary beyond zero-recoil lattice QCD calculations on the $|V_{cb}|$ determinations. Additionally, we present the lepton flavor universality ratio $R_{eμ} = \mathcal{B}(B \to D^* e \barν_e) / \mathcal{B}(B \to D^* μ\barν_μ) = 0.990 \pm 0.021 \pm 0.023$, the electron and muon forward-backward asymmetry and their difference $ΔA_{FB}=0.022\pm0.026\pm 0.007$, and the electron and muon $D^*$ longitudinal polarization fraction and their difference $ΔF_L^{D^*} = 0.034 \pm 0.024 \pm 0.007$. The uncertainties quoted correspond to the statistical and systematic uncertainties, respectively.

hep-ex↗

arXiv2023

Search for rare decays $B^{+} \to D_{s}^{(\ast)+}η$, $D_{s}^{(\ast)+}\bar{K}^{0}$, $D^{+}η$, and $D^{+}K^{0}$

We present a study of rare decay modes $B^{+} \to D_{s}^{+}h^{0}$, $B^{+} \to D_{s}^{\ast+}h^{0}$, and $B^{+} \to D^{+}h^{0}$, where $h^{0}$ denotes the neutral mesons $η$ or $K^{0}$, using a data sample of $(772 \pm 10 ) \times 10^{6}$ $B\bar{B}$ events produced at the $Υ(4S)$ resonance. The data were collected by the Belle detector operating at the asymmetric-energy KEKB collider. We observe no evidence for these decays, so we provide upper limits at the 90$\%$ confidence level on the branching fractions of $B^{+} \to D_{s}^{+}h^{0}$, $D_{s}^{\ast+}h^{0}$, and $D^{+}h^{0}$ decay modes. Along with rare decay modes, we report improved measurements of the color-suppressed decay branching fractions $\mathcal{B}(\bar{B}^{0} \to D^{0}η)$ = (26.6 $\pm$ 1.2 $\pm$ 2.1) $\times$ $10^{-5}$ and $\mathcal{B}(\bar{B}^{0} \to D^{0}\bar{K}^{0})$ = (5.6 $\pm$ 0.5 $\pm$ 0.2) $\times$ $10^{-5}$. The first and second uncertainties are statistical and systematic, respectively.

hep-ex↗

arXiv2022

Evidence for the singly Cabibbo-suppressed decay $Ω^0_c\toΞ^-π^+$ and search for $Ω^0_c\toΞ^-K^+$ and $Ω^-K^+$ decays at Belle

Using a data sample of 980 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider, we study for the first time the singly Cabibbo-suppressed decays $Ω^0_c\toΞ^{-}π^{+}$ and $Ω^-K^+$ and the doubly Cabibbo-suppressed decay $Ω^0_c\to Ξ^- K^{+}$. Evidence for an $Ω^0_c$ signal in the $Ω^0_c\toΞ^-π^+$ mode is reported with a significance of $4.5σ$ including systematic uncertainties. The ratio of branching fractions to the normalization mode $Ω_c^0\to Ω^-π^+$ is measured to be $${\cal B}(Ω_{c}^{0} \to Ξ^{-} π^{+} )/{\cal B}(Ω_c^0\to Ω^-π^+)=0.253\pm 0.053({\rm stat.})\pm 0.030({\rm syst.}).$$ No significant signals of $Ω^0_c\toΞ^-K^+$ and $Ω^-K^+$ modes are found. The upper limits at $90\%$ confidence level on ratios of branching fractions are determined to be $${\cal B}(Ω_{c}^{0} \to Ξ^{-} K ^{+})/{\cal B}(Ω_c^0\to Ω^-π^+) < 0.070$$ and $${\cal B}(Ω_{c}^{0} \to Ω^{-}K^{+})/{\cal B}(Ω_c^0\to Ω^-π^+) < 0.29.$$

hep-ex↗

arXiv2022

Measurement of branching fractions of $Λ_c^+\to{}pK_S^0K_S^0$ and $Λ_c^+\to{}pK_S^0η$ at Belle

We present a study of a singly Cabibbo-suppressed decay $Λ_c^+\to{}pK_S^0K_S^0$ and a Cabibbo-favored decay $Λ_c^+\to{}pK_S^0η$ based on 980 $\rm fb^{-1}$ of data collected by the Belle detector, operating at the KEKB energy-asymmetric $e^+e^-$ collider. We measure their branching fractions relative to $Λ_c^+\to{}pK_S^0$: $\mathcal{B}(Λ_c^+\to{}pK_S^0K_S^0)/\mathcal{B}(Λ_c^+\to{}pK_S^0)={(1.48 \pm 0.08 \pm 0.04)\times 10^{-2}}$ and $\mathcal{B}(Λ_c^+\to{}pK_S^0η)/\mathcal{B}(Λ_c^+\to{}pK_S^0)={(2.73\pm 0.06\pm 0.13)\times 10^{-1}}$. Combining with the world average $\mathcal{B}(Λ_c^+\to{}pK_S^0)$, we have the absolute branching fractions: $\mathcal{B}(Λ_c^+\to{}pK_S^0K_S^0) = {(2.35\pm 0.12\pm 0.07 \pm 0.12 )\times 10^{-4}}$ and $\mathcal{B}(Λ_c^+\to{}pK_S^0η) = {(4.35\pm 0.10\pm 0.20 \pm 0.22 )\times 10^{-3}}$. The first and second uncertainties are statistical and systematic, respectively, while the third ones arise from the uncertainty on $\mathcal{B}(Λ_c^+\to{}pK_S^0)$. The mode $Λ_c^+\to{}pK_S^0K_S^0$ is observed for the first time and has a statistical significance of $>\!10σ$. The branching fraction of $Λ_c^+\to{}pK_S^0η$ has been measured with a threefold improvement in precision over previous results and is found to be consistent with the world average.

hep-ex↗

arXiv2022

Measurement of the branching fractions for Cabibbo-suppressed decays $D^{+}\to K^{+} K^{-}π^{+}π^{0}$ and $D_{(s)}^{+}\to K^{+}π^{-}π^{+}π^{0}$ at Belle

We present measurements of the branching fractions for the singly Cabibbo-suppressed decays $D^+\to K^{+}K^{-}π^{+}π^{0}$ and $D_s^{+}\to K^{+}π^{-}π^{+}π^{0}$, and the doubly Cabibbo-suppressed decay $D^{+}\to K^{+}π^{-}π^{+}π^{0}$, based on 980 ${\rm fb}^{-1}$ of data recorded by the Belle experiment at the KEKB $e^{+}e^{-}$ collider. We measure these modes relative to the Cabibbo-favored modes $D^{+}\to K^{-}π^{+}π^{+}π^{0}$ and $D_s^{+}\to K^{+}K^{-}π^{+}π^{0}$. Our results for the ratios of branching fractions are $B(D^{+}\to K^{+}K^{-}π^{+}π^{0})/B(D^{+}\to K^{-}π^{+}π^{+}π^{0}) = (11.32 \pm 0.13 \pm 0.26)\%$, $B(D^{+}\to K^{+}π^{-}π^{+}π^{0})/B(D^{+}\to K^{-}π^{+}π^{+}π^{0}) = (1.68 \pm 0.11\pm 0.03)\%$, and $B(D_s^{+}\to K^{+}π^{-}π^{+}π^{0})/B(D_s^{+}\to K^{+}K^{-}π^{+}π^{0}) = (17.13 \pm 0.62 \pm 0.51)\%$, where the uncertainties are statistical and systematic, respectively. The second value corresponds to $(5.83\pm 0.42)\times\tan^4θ_C$, where $θ_C$ is the Cabibbo angle; this value is larger than other measured ratios of branching fractions for a doubly Cabibbo-suppressed charm decay to a Cabibbo-favored decay. Multiplying these results by world average values for $B(D^{+}\to K^{-}π^{+}π^{+}π^{0})$ and $B(D_s^{+}\to K^{+}K^{-}π^{+}π^{0})$ yields $B(D^{+}\to K^{+}K^{-}π^{+}π^{0})= (7.08\pm 0.08\pm 0.16\pm 0.20)\times10^{-3}$, $B(D^{+}\to K^{+}π^{-}π^{+}π^{0})= (1.05\pm 0.07\pm 0.02\pm 0.03)\times10^{-3}$, and $B(D_s^{+}\to K^{+}π^{-}π^{+}π^{0}) = (9.44\pm 0.34\pm 0.28\pm 0.32)\times10^{-3}$, where the third uncertainty is due to the branching fraction of the normalization mode. The first two results are consistent with, but more precise than, the current world averages. The last result is the first measurement of this branching fraction.

hep-ex↗

arXiv2022

Search for the lepton flavour violating decays $B^{+} \to K^{+} τ^\pm \ell^\mp$ ($\ell = e, μ$) at Belle

We present a search for the lepton-flavour-violating decays $B^+ \to K^+ τ^\pm \ell^\mp$, with $\ell = (e, μ)$, using the full data sample of $772 \times 10^6$ $B\overline{B}$ pairs recorded by the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We use events in which one $B$ meson is fully reconstructed in a hadronic decay mode. We find no evidence for $B^\pm \to K^\pm τ\ell$ decays and set upper limits on their branching fractions at the 90% confidence level in the $(1$-$3) \times 10^{-5}$ range. The obtained limits are the world's best results.

hep-ex↗

arXiv2022

Measurements of the branching fractions $\mathcal{B} (\bar{B}{}^0 \to D^{+} π^-)$ and $\mathcal{B} (\bar{B}{}^0 \to D^{+} K^-)$ and tests of QCD factorization

Using $(771.6 \pm 10.6) \times 10^6$ $B\bar{B}$ meson pairs recorded by the Belle experiment at the KEKB $e^+ e^-$ collider, we report the branching fractions $\mathcal{B}(\bar{B}^0 \to D^{*+} π^-) = (2.62 \pm 0.02 \pm 0.09)\times 10^{-3}$ and $\mathcal{B}(\bar{B}^0 \to D^{*+} K^-) = (2.22 \pm 0.06 \pm 0.08)\times 10^{-4}$; the quoted uncertainties are statistical and systematic, respectively. A measurement of the ratio of these branching fractions is also presented, $\mathcal{R}_{K/π}=\mathcal{B}(\bar{B} \to D^{*+}K^-) /\mathcal{B}( \bar{B} \to D^{*+}π^-) = (8.41 \pm 0.24 \pm 0.13)\times 10^{-2}$, where systematic uncertainties due to the $D^{*+}$ meson reconstruction cancel out. Furthermore, we report a new QCD factorization test based on the measured ratios for $\bar{B} \to D^{*+}h^-$ and $\bar{B} \to D^{*+}\ell^-ν$ decays at squared momentum transfer values equivalent to the mass of the $h = π$ or $K$ hadron. The parameters $|a_1(h)|$ are measured to be $|a_1(π)|= 0.884 \pm 0.004 \pm 0.003 \pm 0.016$ and $|a_1(K)|=0.913 \pm 0.019 \pm 0.008 \pm 0.013$, where the last uncertainties account for all external inputs. These values are approximately $15\%$ lower than those expected from theoretical predictions. Subsequently, flavor $SU(3)$ symmetry is tested by measuring the ratios for pions and kaons, $|a_1(K)|^2/ |a_1(π)|^2=1.066 \pm 0.042 \pm 0.018 \pm 0.023$, as well as for different particle species. The ratio is consistent with unity and therefore no evidence for $SU(3)$ symmetry breaking effects is found at the $5\%$ precision level.

hep-ex↗

arXiv2022

First search for the weak radiative decays $Λ_c^+ \to Σ^+ γ$ and $Ξ_c^0 \to Ξ^0 γ$

We present the first search for the weak radiative decays $Λ_c^+ \to Σ^+ γ$ and $Ξ_c^0 \to Ξ^0 γ$ using a data sample of 980~fb$^{-1}$ collected by the Belle detector operating at the KEKB asymmetric-energy $e^+e^-$ collider. There are no evident $Λ_c^+ \to Σ^+ γ$ or $Ξ_c^0 \to Ξ^0 γ$ signals. Taking the decays $Λ_c^+ \to p K^- π^+$ and $Ξ_c^0 \to Ξ^- π^+$ as normalization channels, the upper limits at 90\% credibility level on the ratios of branching fractions ${\cal B}(Λ_c^+ \to Σ^+ γ)/{\cal B}(Λ_c^+ \to p K^{-} π^+) < 4.0 \times 10^{-3}$ and ${\cal B}(Ξ_c^0 \to Ξ^0 γ)/{\cal B}(Ξ_c^0 \to Ξ^- π^+) < 1.2 \times 10^{-2}$ are determined. We obtain the upper limits at 90\% credibility level on the absolute branching fractions ${\cal B}(Λ_c^+ \to Σ^+ γ) < 2.6 \times 10^{-4}$ and ${\cal B}(Ξ_c^0 \to Ξ^0 γ) < 1.8 \times 10^{-4}$.

hep-ex↗

arXiv2022

Evidence of a new excited charmed baryon decaying to $Σ_{c}(2455)^{0,++} π^{\pm}$

We present the study of $\bar{B}^{0} \to Σ_{c}(2455)^{0,++} π^{\pm} \bar{p}$ decays based on $772\times 10^{6}$ $B\bar{B}$ events collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. The $Σ_{c}(2455)^{0,++} $ candidates are reconstructed via their decay to $Λ_{c}^{+} π^{\mp}$ and $Λ_{c}^{+}$ decays to $pK^{-}π^{+},~pK_{S}^{0},$ and $Λπ^{+}$ final states. The corresponding branching fractions are measured to be ${\cal B}(\bar{B}^{0} \to Σ_{c}(2455)^{0} π^{+} \bar{p}) = (1.09 \pm 0.06 \pm 0.07)\times10^{-4}$ and ${\cal B}(\bar{B}^{0} \to Σ_{c}(2455)^{++} π^{-} \bar{p}) = (1.84\pm 0.11 \pm 0.12)\times 10^{-4}$, which are consistent with the world average values with improved precision. A new structure is found in the $M_{Σ_{c}(2455)^{0,++}π^{\pm}}$ spectrum with a significance of $4.2σ$ including systematic uncertainty. The structure is possibly an excited $Λ_{c}^{+}$ and is tentatively named $Λ_{c}(2910)^{+}$. Its mass and width are measured to be $(2913.8 \pm 5.6 \pm 3.8)$ MeV/$c^{2}$ and $(51.8\pm20.0 \pm 18.8)$ MeV, respectively. The products of branching fractions for the $Λ_{c}(2910)^{+}$ are measured to be ${\cal B}(\bar{B}^{0} \to Λ_{c}(2910)^{+}\bar{p})\times{\cal B}(Λ_{c}(2910)^{+} \to Σ_{c}(2455)^{0}π^{+}) = (9.5 \pm 3.6 \pm 1.6)\times 10^{-6}$ and ${\cal B}(\bar{B}^{0} \to Λ_{c} (2910)^{+}\bar{p})\times {\cal B}(Λ_{c}(2910)^{+} \to Σ_{c}(2455)^{++}π^{-}) = (1.24 \pm 0.35 \pm 0.10)\times 10^{-5}$. Here, the first and second uncertainties are statistical and systematic, respectively.

hep-ex↗

arXiv2022

Measurement of the branching fraction of $Ξ_{c}^{0}\to Λ_{c}^{+}π^{-}$ at Belle

Based on a data sample of 983 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider, we present the study of the heavy-flavor-conserving decay $Ξ_{c}^{0}\to Λ_{c}^{+}π^{-}$ with $Λ_{c}^{+}$ reconstructed via its $pK^{-} π^{+}$ decay mode. The branching fraction ratio $\mathcal{B}(Ξ_{c}^{0}\to Λ_{c}^{+}π^{-})/\mathcal{B}(Ξ_{c}^{0}\to Ξ^{-}π^{+})$ is measured to be $0.38 \pm 0.04 \pm 0.04$. Combing with the world average value of $\mathcal{B}(Ξ_{c}^{0}\to Ξ^{-}π^{+})$, the branching fraction $\mathcal{B}(Ξ_{c}^{0}\to Λ_{c}^{+}π^{-})$ is deduced to be $(0.54 \pm 0.05 \pm 0.05 \pm 0.12)\%$. Here, the uncertainties above are statistical, systematic, and from $\mathcal{B}(Ξ_c^{0} \to Ξ^{-}π^{+})$, respectively.

hep-ex↗

arXiv2022

Radio Transients and Variables in the Tenth Deeper, Wider, Faster Observing Run

The Deeper, Wider, Faster (DWF) program coordinates observations with telescopes across the electromagnetic spectrum, searching for transients on timescales of milliseconds to days. The tenth DWF observing run was carried out in near real-time during September 2021 and consisted of six consecutive days of observations of the NGC 6744 galaxy group and a field containing the repeating fast radio burst FRB190711 with the Australian Square Kilometre Array Pathfinder, the Dark Energy Camera, the Hard X-ray Modulation Telescope and the Parkes 64m "Murriyang" radio telescope. In this work we present the results of an image-domain search for transient, variable and circularly polarised sources carried out with ASKAP using data from the observing run, along with test observations prior to the run and follow-up observations carried out during and after the run. We identified eight variable radio sources, consisting of one pulsar, six stellar systems (five of which exhibit circularly polarised emission) and one previously uncatalogued source. Of particular interest is the detection of pulses from the ultra-cool dwarf SCR J1845-6357 with a period of $14.2\pm 0.3$ h, in good agreement with the known optical rotation period, making this the slowest rotating radio-loud ultra-cool dwarf discovered.

astro-ph.HE↗

arXiv2022

Measured proton electromagnetic structure deviates from theoretical predictions

The visible world is founded on the proton, the only composite building block of matter that is stable in nature. Consequently, understanding the formation of matter relies on explaining the dynamics and the properties of the proton's bound state.A fundamental property of the proton involves the response of the system to an external electromagnetic field. It is characterized by the electromagnetic polarizabilities that describe how easily the charge and magnetization distributions inside the system are distorted by the electromagnetic field. Moreover, the generalized polarizabilities map out the resulting deformation of the densities in a proton subject to an electromagnetic field. They disclose essential information about the underlying system dynamics and provide a key for decoding the proton structure in terms of the theory of the strong interaction that binds its elementary quark and gluon constituents. Of particular interest is a puzzle in the electric generalized polarizability of the proton that remains unresolved for two decades. Here we report measurements of the proton's electromagnetic generalized polarizabilities at low four-momentum transfer squared. We show evidence of an anomaly to the behaviour of the proton's electric generalized polarizability that contradicts the predictions of nuclear theory and derive its signature in the spatial distribution of the induced polarization in the proton. The reported measurements suggest the presence of a new, not-yet-understood dynamical mechanism in the proton and present notable challenges to the nuclear theory.

nucl-ex↗

arXiv2022

Measurement of the branching fractions of the $B^+ \to η\ell^+ ν_{\ell} $ and $B^+ \to η^{\prime} \ell^+ ν_{\ell} $ decays with signal-side only reconstruction in the full $q^2$ range

The branching fractions of the decays $B^{+} \to η\ell^{+} ν_{\ell}$ and $B^{+} \to η^{\prime} \ell^{+} ν_{\ell}$ are measured, where $\ell$ is either an electron or a muon, using a data sample of $711\,{\rm fb}^{-1}$ containing $772 \times 10^6 B\bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. To reduce the dependence of the result on the form factor model, the measurement is performed over the entire $q^2$ range. The resulting branching fractions are ${\cal B}(B^{+} \rightarrow η\ell^{+} ν_{\ell}) = (2.83 \pm 0.55_{\rm (stat.)} \pm 0.34_{\rm (syst.)}) \times 10^{-5}$ and ${\cal B}(B^{+} \rightarrow η' \ell^{+} ν_{\ell}) = (2.79 \pm 1.29_{\rm (stat.)} \pm 0.30_{\rm (syst.)}) \times 10^{-5}$.

hep-ex↗

arXiv2022

Search for $Z^{'} \rightarrow μ^{+} μ^{-}$ in the $L_μ{-} L_τ$ gauge-symmetric model at Belle

We search for a new gauge boson $Z'$ that couples only to heavy leptons and their corresponding neutrinos in the process $e^{+} e^{-} \rightarrow Z'(\rightarrow μ^{+}μ^{-}) μ^{+}μ^{-}$, using a 643 fb$^{-1}$ data sample collected by the Belle experiment at or near the $Υ(1S,2S,3S,4S,5S)$ resonances at the KEKB collider. For the first time, effects due to initial state radiation are used in estimating the detection efficiency. No signal is observed in the mass range of 0.212 \ -- 10 GeV/${\it c}^2$ and we set an upper limit on the coupling strengh, $g'$, constraining $Z'$ as a possible contributor to the anomalous magnetic dipole moment of muon.

hep-ex↗

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.

hep-ex↗

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.

hep-ex↗

arXiv2022

Measurement of the branching fraction and $CP$ asymmetry for $B\to\bar{D}^{0} π$ decays

We measure the branching fractions and $CP$ asymmetries for the decays $B^{0}\to \bar{D}^{0}π^{0}$ and $B^{+}\to \bar{D}^{0}π^{+}$, using a data sample of $772\times 10^{6}$ $B\bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^{+}e^{-}$ collider. The branching fractions obtained and direct $CP$ asymmetries are $\mathcal{B}(B^{0}\to \bar{D}^{0}π^{0}) = [2.70 \pm 0.06~ \text{(stat.)} \pm 0.10~ \text{(syst.)}] \times 10^{-4}$, $\mathcal{B}(B^{+}\to \bar{D}^{0}π^{+}) = [4.53 \pm 0.02~ \text{(stat.)} \pm 0.15~ \text{(syst.)}] \times 10^{-3}$, $ {\cal A}_{CP}(B^{0}\to \bar{D}^{0}π^{0}) = [+0.42 \pm 2.05~ \text{(stat.)} \pm 1.22~ \text{(syst.)}]\%$, and $ {\cal A}_{CP}(B^{+}\to \bar{D}^{0}π^{+}) = [+0.19 \pm 0.36~ \text{(stat.)} \pm 0.57~ \text{(syst.)}]\%$. The measurements of $\mathcal{B}$ are the most precise to date and are in good agreement with previous results, as is the measurement of ${\cal A}_{CP}(B^{+}\to \bar{D}^{0}π^{+})$. The measurement of ${\cal A}_{CP}$ for $B^{0}\to \bar{D}^{0}π^{0}$ is the first for this mode, and the value is consistent with Standard Model expectations.

hep-ex↗

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 $M_{K_S^0 K_S^0}$.

hep-ex↗