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We present the results of a search for the charged-lepton-flavor violating decays B ⁰→ K ^(*0) τ ^(±) ℓ ^(∓) , where ℓ ^(∓)is either an electron or a muon. The results are based on 365 fb ⁻¹and 711 fb ⁻¹datasets collected with the Belle II and Belle detectors, respectively. We use an exclusive hadronic B-tagging technique, and search for a signal decay in the system recoiling against a fully reconstructed B meson. We find no evidence for B ⁰→ K ^(*0) τ ^(±) ℓ ^(∓)decays and set upper limits on the branching fractions in the range of (2.9–6.4)×10 ⁻⁵at 90% confidence level. 19 pages, 4 figures

We present measurements ofB → K^(*)(892)γdecays using365 \\rm fb⁻¹of data collected from 2019 to 2022 by the Belle II experiment at the SuperKEKB asymmetric-energye⁺e⁻collider. The data sample contains(387 ± 6) × 10⁶Υ(4S)events. We measure branching fractions ( 𝓑 ) andC\\!{P}{}{a}symmetries ( 𝓐_(C\\!P) ) for bothB⁰→ K^(*0)γandB⁺→ K^(*+)γdecays. The difference inC\\!{P}{}{a}symmetries ( Δ𝓐_(C\\!P) ) and the isospin asymmetry ( Δ₀₊ ) between these neutral and charged channels are also measured. We obtain the following branching fractions andC\\!{P}{}{a}symmetries:𝓑 (B⁰ → K^(*0)γ) = (4.14 ± 0.10 ± 0.11 ) × 10⁻⁵ ,𝓑 (B⁺ → K^(*+)γ) = (4.04 ± 0.13 ^(+0.13)_(-0.15) )× 10⁻⁵ ,𝓐_(C\\!P) (B⁰ → K^(*0)γ) = (-3.3 ± 2.3 ± 0.4 )% , and𝓐_(C\\!P) (B⁺ → K^(*+)γ) = (-0.7 ± 2.9 ± 0.5 )% . The measured difference inC\\!{P}{}{a}symmetries isΔ𝓐_(C\\!P) = (+2.6 ± 3.8 ± 0.6 )% , and the measured isospin asymmetry isΔ₀₊ = (+4.8 ± 2.0 ± 1.8 )% . The first uncertainties listed are statistical and the second are systematic. These results are consistent with world-average values and theory predictions.

We perform the first search for$C\\!P$violation in${D_{(s)}^{+}\\to{}K_{S}^{0}K^{-}\\pi^{+}\\pi^{+}}$decays. We use a combined data set from the Belle and Belle II experiments, which study$e^+e^-$collisions at center-of-mass energies at or near the$\\Upsilon(4S)$resonance. We use 980 fb $^{-1}$of data from Belle and 428 fb $^{-1}$of data from Belle~II. We measure six$C\\!P$ -violating asymmetries that are based on triple products and quadruple products of the momenta of final-state particles, and also the particles' helicity angles. We obtain a precision at the level of 0.5% for$D^+\\to{}K_{S}^{0}K^{-}\\pi^{+}\\pi^{+}$decays, and better than 0.3% for$D^+_{s}\\to{}K_{S}^{0}K^{-}\\pi^{+}\\pi^{+}$decays. No evidence of$C\\!P$violation is found. Our results for the triple-product asymmetries are the most precise to date for singly-Cabibbo-suppressed$D^+$decays. Our results for the other asymmetries are the first such measurements performed for charm decays. 21 pages, 10 figures

We report measurements of the absolute branching fractions𝓑(B_(s)⁰ → D_(s)^(±) X) ,𝓑(B_(s)⁰ → D⁰/D̄⁰ X) , and𝓑(B_(s)⁰ → D^(±) X) , where the latter is measured for the first time. The results are based on a 121.4 fb ⁻¹data sample collected at theΥ(10860)resonance by the Belle detector at the KEKB asymmetric-energye⁺ e⁻collider. We reconstruct oneB_(s)⁰meson ine⁺e⁻ → Υ(10860) → B_(s)^(*) B̄_(s)^(*)events and measure yields ofD_(s)⁺ ,D⁰ , andD⁺mesons in the rest of the event. We obtain𝓑(B_(s)⁰ → D_(s)^(±) X) = (68.6 ± 7.2 ± 4.0)% ,𝓑(B_(s)⁰ → D⁰/D̄⁰ X) = (21.5 ± 6.1 ± 1.8)% , and𝓑(B_(s)⁰ → D^(±) X) = (12.6 ± 4.6 ± 1.3)% , where the first uncertainty is statistical and the second is systematic. Averaging with previous Belle measurements gives𝓑(B_(s)⁰ → D_(s)^(±) X) = (63.4 ± 4.5 ± 2.2)%and𝓑(B_(s)⁰ → D⁰/D̄⁰ X) = (23.9 ± 4.1 ± 1.8)% . For theB_(s)⁰production fraction at theΥ(10860) , we findf_(s) = (21.4^(+1.5)_(-1.7))% .

Using data samples of 983.0 fb − 1 and 427.9 fb − 1 accumulated with the Belle and Belle II detectors operating at the KEKB and SuperKEKB asymmetric-energy e + e − colliders, singly Cabibbo-suppressed decays$ {\\Xi}_c^{+}\\to p{K}_S^0 $Ξ c + → p K S 0 ,$ {\\Xi}_c^{+}\\to \\Lambda {\\pi}^{+} $Ξ c + → Λ π + , and$ {\\Xi}_c^{+}\\to {\\Sigma}^0{\\pi}^{+} $Ξ c + → Σ 0 π + are observed for the first time. The ratios of branching fractions of$ {\\Xi}_c^{+}\\to p{K}_S^0 $Ξ c + → p K S 0 ,$ {\\Xi}_c^{+}\\to \\Lambda {\\pi}^{+} $Ξ c + → Λ π + , and$ {\\Xi}_c^{+}\\to {\\Sigma}^0{\\pi}^{+} $Ξ c + → Σ 0 π + relative to that of$ {\\Xi}_c^{+}\\to {\\Xi}^{-}{\\pi}^{+}{\\pi}^{+} $Ξ c + → Ξ − π + π + are measured to be$ {\\displaystyle \\begin{array}{c}\\frac{\\mathcal{B}\\left({\\Xi}_c^{+}\\to p{K}_S^0\\right)}{\\mathcal{B}\\left({\\Xi}_c^{+}\\to {\\Xi}^{-}{\\pi}^{+}{\\pi}^{+}\\right)}=\\left(2.47\\pm 0.16\\pm 0.07\\right)\\%,\\\ {}\\frac{\\mathcal{B}\\left({\\Xi}_c^{+}\\to \\Lambda {\\pi}^{+}\\right)}{\\mathcal{B}\\left({\\Xi}_c^{+}\\to {\\Xi}^{-}{\\pi}^{+}{\\pi}^{+}\\right)}=\\left(1.56\\pm 0.14\\pm 0.09\\right)\\%,\\\ {}\\frac{\\mathcal{B}\\left({\\Xi}_c^{+}\\to {\\Sigma}^0{\\pi}^{+}\\right)}{\\mathcal{B}\\left({\\Xi}_c^{+}\\to {\\Xi}^{-}{\\pi}^{+}{\\pi}^{+}\\right)}=\\left(4.13\\pm 0.26\\pm 0.22\\right)\\%.\\end{array}} $B Ξ c + → p K S 0 B Ξ c + → Ξ − π + π + = 2.47 ± 0.16 ± 0.07 % , B Ξ c + → Λ π + B Ξ c + → Ξ − π + π + = 1.56 ± 0.14 ± 0.09 % , B Ξ c + → Σ 0 π + B Ξ c + → Ξ − π + π + = 4.13 ± 0.26 ± 0.22 % . Multiplying these values by the branching fraction of the normalization channel,$ \\mathcal{B}\\left({\\Xi}_c^{+}\\to {\\Xi}^{-}{\\pi}^{+}{\\pi}^{+}\\right)=\\left(2.9\\pm 1.3\\right)\\% $B Ξ c + → Ξ − π + π + = 2.9 ± 1.3 % , the absolute branching fractions are determined to be$ {\\displaystyle \\begin{array}{c}\\mathcal{B}\\left({\\Xi}_c^{+}\\to p{K}_S^0\\right)=\\left(7.16\\pm 0.46\\pm 0.20\\pm 3.21\\right)\\times {10}^{-4},\\\ {}\\mathcal{B}\\left({\\Xi}_c^{+}\\to \\Lambda {\\pi}^{+}\\right)=\\left(4.52\\pm 0.41\\pm 0.26\\pm 2.03\\right)\\times {10}^{-4},\\\ {}\\mathcal{B}\\left({\\Xi}_c^{+}\\to {\\Sigma}^0{\\pi}^{+}\\right)=\\left(1.20\\pm 0.08\\pm 0.07\\pm 0.54\\right)\\times {10}^{-3}.\\end{array}} $B Ξ c + → p K S 0 = 7.16 ± 0.46 ± 0.20 ± 3.21 × 10 − 4 , B Ξ c + → Λ π + = 4.52 ± 0.41 ± 0.26 ± 2.03 × 10 − 4 , B Ξ c + → Σ 0 π + = 1.20 ± 0.08 ± 0.07 ± 0.54 × 10 − 3 . The first and second uncertainties above are statistical and systematic, respectively, while the third ones arise from the uncertainty in$ \\mathcal{B}\\left({\\Xi}_c^{+}\\to {\\Xi}^{-}{\\pi}^{+}{\\pi}^{+}\\right) $B Ξ c + → Ξ − π + π + .

We report measurements of thee⁺e⁻ → BB̄ ,BB̄^(*) , andB^(*)B̄^(*)cross sections at four energies, 10653, 10701, 10746 and 10805 MeV, using data collected by the Belle II experiment. We reconstruct oneBmeson in a large number of hadronic final states and use its momentum to identify the production process. In the first2-5MeV aboveB^(*)B̄^(*)threshold, thee⁺e⁻ → B^(*)B̄^(*)cross section increases rapidly. This may indicate the presence of a pole close to the threshold.

We report the first measurement of the inclusive e ⁺ e ⁻ → bb̅ → D_(s)^(±) X and e ⁺ e ⁻ → bb̅ → D ⁰ / D̅⁰ X cross sections in the energy range from 10.63 to 11.02 GeV. Based on these results, we determine σ(e ⁺ e ⁻ → B_(s)⁰B̅_(s)⁰ X) and σ(e ⁺ e ⁻ → BB̅ X) in the same energy range. We measure the fraction of B_(s)⁰ events at Υ(10860) to be f _(s)= ( 22.0_(-2.1)^(+2.0) )%. We determine also the ratio of the B_(s)⁰ inclusive branching fractions 𝓑 ( B_(s)⁰ → D ⁰ / D̅⁰ X)/ 𝓑 ( B_(s)⁰ → D_(s)^(±) X) = 0.416 ± 0.018 ± 0.092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energy e ⁺ e ⁻collider.[graphic not available: see fulltext]

We report the first measurement of the inclusive e + e − →$$ b\\overline{b} $$b b ¯ →$$ {D}_s^{\\pm } $$D s ± X and e + e − →$$ b\\overline{b} $$b b ¯ → D 0 /$$ {\\overline{D}}^0 $$D ¯ 0 X cross sections in the energy range from 10 . 63 to 11 . 02 GeV. Based on these results, we determine σ ( e + e − →$$ {B}_s^0{\\overline{B}}_s^0 $$B s 0 B ¯ s 0 X ) and σ ( e + e − →$$ B\\overline{B} $$B B ¯ X ) in the same energy range. We measure the fraction of$$ {B}_s^0 $$B s 0 events at Υ(10860) to be f 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 → D 0 /$$ {\\overline{D}}^0 $$D ¯ 0 X ) /$$ \\mathcal{B} $$B ($$ {B}_s^0 $$B s 0 →$$ {D}_s^{\\pm } $$D s ± X ) = 0 . 416 ± 0 . 018 ± 0 . 092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energy e + e − collider.

We report the first measurement of the inclusive e+e- → bb̄ → D^(±)_(s) X and e+e- → bb̄ → D0 / D̅⁰ X cross sections in the energy range from 10.63 to 11.02 GeV. Based on these results, we determine σ(e+e- → B_(s)⁰B̅_(s)⁰ X) and σ(e+e- → BB̅ X) in the same energy range. We measure the fraction of B_(s)⁰ events at Υ(10860) to be fs = (22.0_(-2.1)^(+2.0))%. We determine also the ratio of the B_(s)⁰ inclusive branching fractions 𝓑(B_(s)⁰ → D0/ D̅⁰X)/𝓑(B_(s)⁰ → D_(s)^(±)X) = 0.416 ± 0.018 ± 0.092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider.

Using a data sample of 980 fb ⁻¹collected with the Belle detector at the KEKB asymmetric-energye⁺e⁻collider, we study for the first time the singly Cabibbo-suppressed decaysΩ⁰_(c)\\toΞ{⁻}{π}{⁺}andΩ⁻K⁺and the doubly Cabibbo-suppressed decayΩ⁰_(c)→ Ξ⁻ K⁺ . Evidence for anΩ⁰_(c)signal in theΩ⁰_(c)\\toΞ{⁻}{π}{⁺}mode is reported with a significance of4.5σincluding systematic uncertainties. The ratio of branching fractions to the normalization modeΩ_(c)⁰→ Ω⁻π⁺is measured to be 𝓑(Ω_(c)⁰ → Ξ⁻ π⁺ )/𝓑(Ω_(c)⁰→ Ω⁻π⁺)=0.253± 0.053(\\rm stat.)± 0.030(\\rm syst.). No significant signals ofΩ⁰_(c)\\toΞ{⁻}{K}{⁺}andΩ⁻K⁺modes are found. The upper limits at90%confidence level on ratios of branching fractions are determined to be 𝓑(Ω_(c)⁰ → Ξ⁻ K ⁺)/𝓑(Ω_(c)⁰→ Ω⁻π⁺) < 0.070 and 𝓑(Ω_(c)⁰ → Ω⁻K⁺)/𝓑(Ω_(c)⁰→ Ω⁻π⁺) < 0.29.