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1. Measurements of the branching fractions of $${\Xi }_{c}^{+}\to {\Sigma }^{+}{K}_{S}^{0}$$, $${\Xi }_{c}^{+}\to {\Xi }^{0}{\pi }^{+}$$, and $${\Xi }_{c}^{+}\to {\Xi }^{0}{K}+$$ at Belle and Belle II

   https://doi.org/10.1007/JHEP08(2025)195  

   Adachi, I; Ahn, J K; Ahn, Y; Akopov, N; Alghamdi, S; Alhakami, M; Althubiti, N; Amos, K; Anh_Ky, N; Antonioli, C; et al (August 2025, Journal of High Energy Physics)

   A<sc>bstract</sc> Using 983.0 fb⁻¹and 427.9 fb⁻¹data samples collected with the Belle and Belle II detectors at the KEKB and SuperKEKB asymmetric energye⁺e⁻colliders, respectively, we present studies of the Cabibbo-favored$${\Xi }_{c}^{+}$$decays$${\Xi }_{c}^{+}\to {\Sigma }^{+}{K}_{S}^{0}$$and$${\Xi }_{c}^{+}\to {\Xi }^{0}{\pi }^{+}$$, and the singly Cabibbo-suppressed decay$${\Xi }_{c}^{+}\to {\Xi }^{0}{K}^{+}$$. The ratios of branching fractions of$${\Xi }_{c}^{+}\to {\Sigma }^{+}{K}_{S}^{0}$$and$${\Xi }_{c}^{+}\to {\Xi }^{0}{K}^{+}$$relative to that of$${\Xi }_{c}^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+}$$are measured for the first time, while the ratio$$\mathcal{B}({\Xi }_{c}^{+}\to {\Xi }^{0}{\pi }^{+})/\mathcal{B}({\Xi }_{c}^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+})$$is also determined and improved by an order of magnitude in precision. The measured branching fraction ratios are $$\begin{array}{c}\frac{\mathcal{B}\left({\Xi }_{c}^{+}\to {\Sigma }^{+}{K}_{S}^{0}\right)}{\mathcal{B}\left({\Xi }_{c}^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+}\right)}=0.067\pm 0.007\pm 0.003,\\ \frac{\mathcal{B}\left({\Xi }_{c}^{+}\to {\Xi }^{0}{\pi }^{+}\right)}{\mathcal{B}\left({\Xi }_{c}^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+}\right)}=0.251\pm 0.005\pm 0.010,\\ \frac{\mathcal{B}\left({\Xi }_{c}^{+}\to {\Xi }^{0}{K}^{+}\right)}{\mathcal{B}\left({\Xi }_{c}^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+}\right)}=0.017\pm 0.003\pm 0.001.\end{array}$$ Additionally, the ratio$$\mathcal{B}({\Xi }_{c}^{+}\to {\Xi }^{0}{K}^{+})/\mathcal{B}({\Xi }_{c}^{+}\to {\Xi }^{0}{\pi }^{+})$$is measured to be 0.068±0.010±0.004. Here, the first and second uncertainties are statistical and systematic, respectively. Multiplying the ratios by the branching fraction of the normalization mode,$$\mathcal{B}({\Xi }_{c}^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+})=(2.9\pm 1.3)\%$$, we obtain the following absolute branching fractions $$\begin{array}{c}\mathcal{B}({\Xi }_{c}^{+}\to {\Sigma }^{+}{K}_{S}^{0})=(0.194\pm 0.021\pm 0.009\pm 0.087)\text{\%},\\ \mathcal{B}({\Xi }_{c}^{+}\to {\Xi }^{0}{\pi }^{+})=(0.728\pm 0.014\pm 0.027\pm 0.326)\text{\%},\\ \mathcal{B}({\Xi }_{c}^{+}\to {\Xi }^{0}{K}^{+})=(0.049\pm 0.007\pm 0.003\pm 0.022)\text{\%},\end{array}$$ where the third uncertainties are from$$\mathcal{B}({\Xi }_{c}^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+})$$. 

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2. Measurement of the inclusive branching fractions for $${B}_{s}^{0}$$ decays into D mesons via hadronic tagging

   https://doi.org/10.1007/JHEP04(2025)114  

   Adachi, I; Aggarwal, L; Ahmed, H; Aihara, H; Akopov, N; Aloisio, A; Al_Said, S; Althubiti, N; Anh_Ky, N; Asner, D M; et al (April 2025, Journal of High Energy Physics)

   A<sc>bstract</sc> We report measurements of the absolute branching fractions$$\mathcal{B}\left({B}_{s}^{0}\to {D}_{s}^{\pm }X\right)$$,$$\mathcal{B}\left({B}_{s}^{0}\to {D}^{0}/{\overline{D} }^{0}X\right)$$, and$$\mathcal{B}\left({B}_{s}^{0}\to {D}^{\pm }X\right)$$, where the latter is measured for the first time. The results are based on a 121.4 fb⁻¹data sample collected at the Υ(10860) resonance by the Belle detector at the KEKB asymmetric-energye⁺e⁻collider. We reconstruct one$${B}_{s}^{0}$$meson in$${e}^{+}{e}^{-}\to \Upsilon\left(10860\right)\to {B}_{s}^{*}{\overline{B} }_{s}^{*}$$events and measure yields of$${D}_{s}^{+}$$,D⁰, andD⁺mesons in the rest of the event. We obtain$$\mathcal{B}\left({B}_{s}^{0}\to {D}_{s}^{\pm }X\right)=\left(68.6\pm 7.2\pm 4.0\right)\%$$,$$\mathcal{B}\left({B}_{s}^{0}\to {D}^{0}/{\overline{D} }^{0}X\right)=\left(21.5\pm 6.1\pm 1.8\right)\%$$, and$$\mathcal{B}\left({B}_{s}^{0}\to {D}^{\pm }X\right)=\left(12.6\pm 4.6\pm 1.3\right)\%$$, where the first uncertainty is statistical and the second is systematic. Averaging with previous Belle measurements gives$$\mathcal{B}\left({B}_{s}^{0}\to {D}_{s}^{\pm }X\right)=\left(63.4\pm 4.5\pm 2.2\right)\%$$and$$\mathcal{B}\left({B}_{s}^{0}\to {D}^{0}/{\overline{D} }^{0}X\right)=\left(23.9\pm 4.1\pm 1.8\right)\%$$. For the$${B}_{s}^{0}$$production fraction at the Υ(10860), we find$${f}_{s}=\left({21.4}_{-1.7}^{+1.5}\right)\%$$. 

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3. Measurement of the e+e− → $$ {B}_s^0{\overline{B}}_s^0X $$ cross section in the energy range from 10.63 to 11.02 GeV using inclusive $$ {D}_s^{+} $$ and D0 production

   https://doi.org/10.1007/JHEP08(2023)131  

   Zhukova, V; Mizuk, R; Adachi, I; Aihara, H; Al_Said, S; Asner, D M; Atmacan, H; Aulchenko, V; Aushev, T; Ayad, R; et al (August 2023, Journal of High Energy Physics)

   A<sc>bstract</sc> We report the first measurement of the inclusivee⁺e⁻→$$ b\overline{b} $$ $b\overline{b}$ →$$ {D}_s^{\pm } $$ $D_s^{\pm }$ Xande⁺e⁻→$$ b\overline{b} $$ $b\overline{b}$ → D⁰/$$ {\overline{D}}^0 $$ ${\overline{D}}^0$ Xcross sections in the energy range from 10.63 to 11.02 GeV. Based on these results, we determineσ(e⁺e⁻→$$ {B}_s^0{\overline{B}}_s^0 $$ $B_s^0{\overline{B}}_s^0$ X) andσ(e⁺e⁻→$$ B\overline{B} $$ $B\overline{B}$ X) in the same energy range. We measure the fraction of$$ {B}_s^0 $$ $B_s^0$ events at Υ(10860) to bef_s= ($$ {22.0}_{-2.1}^{+2.0} $$ ${22.0}_{-2.1}^{+2.0}$ )%. We determine also the ratio of the$$ {B}_s^0 $$ $B_s^0$ inclusive branching fractions$$ \mathcal{B} $$ $B$ ($$ {B}_s^0 $$ $B_s^0$ → D⁰/$$ {\overline{D}}^0 $$ ${\overline{D}}^0$ X)/$$ \mathcal{B} $$ $B$ ($$ {B}_s^0 $$ $B_s^0$ →$$ {D}_s^{\pm } $$ $D_s^{\pm }$ X) = 0.416 ± 0.018 ± 0.092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energye⁺e⁻collider. 

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4. Search for $$ {\textrm{B}}_{\textrm{s}}^0 $$ → ℓ∓τ± with the semi-leptonic tagging method at Belle

   https://doi.org/10.1007/JHEP08(2023)178  

   Nayak, L; Nishida, S; Giri, A; Adachi, I; Aihara, H; Asner, D M; Atmacan, H; Aulchenko, V; Aushev, T; Ayad, R; et al (August 2023, Journal of High Energy Physics)

   A<sc>bstract</sc> We present a search for the lepton-flavor-violating decays$$ {B}_s^0 $$ $B_s^0$ →ℓ^∓τ^±, whereℓ=e, μ, using the full data sample of 121 fb⁻¹collected at the Υ(5S) resonance with the Belle detector at the KEKB asymmetric-energye⁺e⁻collider. We use$$ {B}_s^0{\overline{B}}_s^0 $$ $B_s^0{\overline{B}}_s^0$ events in which one$$ {B}_s^0 $$ $B_s^0$ meson is reconstructed in a semileptonic decay mode and the other in the signal mode. We find no evidence for$$ {B}_s^0 $$ $B_s^0$ → ℓ^∓τ^±decays and set upper limits on their branching fractions at 90% confidence level as$$ \mathcal{B} $$ $B$ ($$ {B}_s^0 $$ $B_s^0$ → e^∓τ^±)<14×10⁻⁴and$$ \mathcal{B} $$ $B$ ($$ {B}_s^0 $$ $B_s^0$ → μ^∓τ^±)<7.3×10⁻⁴. Our result represents the first upper limit on the$$ {B}_s^0 $$ $B_s^0$ → e^∓τ^±decay rate. 

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5. Measurement of branching-fraction ratios and CP asymmetries in B± → DCP±K± decays at Belle and Belle II

   https://doi.org/10.1007/JHEP05(2024)212  

   Adachi, I; Aggarwal, L; Aihara, H; Akopov, N; Aloisio, A; Anh_Ky, N; Asner, D M; Atmacan, H; Aushev, T; Aushev, V; et al (May 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> We report results from a study ofB^±→ DK^±decays followed byDdecaying to theCP-even final stateK⁺K⁻and CP-odd final state$$ {K}_S^0{\pi}^0 $$ $K_S^0{\pi }^0$ , whereDis an admixture ofD⁰and$$ {\overline{D}}^0 $$ ${\overline{D}}^0$ states. These decays are sensitive to the Cabibbo-Kobayashi-Maskawa unitarity-triangle angleϕ₃. The results are based on a combined analysis of the final data set of 772×10⁶$$ B\overline{B} $$ $B\overline{B}$ pairs collected by the Belle experiment and a data set of 198×10⁶$$ B\overline{B} $$ $B\overline{B}$ pairs collected by the Belle II experiment, both in electron-positron collisions at the Υ(4S) resonance. We measure the CP asymmetries to be$$ \mathcal{A} $$ $A$ _CP+= (+12.5±5.8±1.4)% and$$ \mathcal{A} $$ $A$ _CP−= (−16.7±5.7±0.6)%, and the ratios of branching fractions to be$$ \mathcal{R} $$ $R$ _CP+= 1.164±0.081±0.036 and$$ \mathcal{R} $$ $R$ _CP−= 1.151±0.074±0.019. The first contribution to the uncertainties is statistical, and the second is systematic. The asymmetries$$ \mathcal{A} $$ $A$ _CP+and$$ \mathcal{A} $$ $A$ _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 <r_B< 0.465. 

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