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We present the novel implementation of a non-differentiable metric approximation and a corresponding loss-scheduling aimed at the search for new particles of unknown mass in high energy physics experiments. We call the loss-scheduling, based on the minimisation of a figure-of-merit related function typical of particle physics, a Punzi-loss function, and the neural network that utilises this loss function a Punzi-net. We show that the Punzi-net outperforms standard multivariate analysis techniques and generalises well to mass hypotheses for which it was not trained. This is achieved by training a single classifier that provides a coherent and optimal classification of all signal hypotheses over the whole search space. Our result constitutes a complementary approach to fully differentiable analyses in particle physics. We implemented this work using PyTorch and provide users full access to a public repository containing all the codes and a training example.

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 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 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 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 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.

A bstract We present a study of$ {\\Xi}_c^0\\to {\\Xi}^0{\\pi}^0 $Ξ c 0 → Ξ 0 π 0 ,$ {\\Xi}_c^0\\to {\\Xi}^0\\eta $Ξ c 0 → Ξ 0 η , and$ {\\Xi}_c^0\\to {\\Xi}^0{\\eta}^{\\prime } $Ξ c 0 → Ξ 0 η ′ decays using the Belle and Belle II data samples, which have integrated luminosities of 980 fb − 1 and 426 fb − 1 , respectively. We measure the following relative branching fractions$ {\\displaystyle \\begin{array}{c}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^0{\\pi}^0\\right)/\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right)=0.48\\pm 0.02\\left(\\textrm{stat}\\right)\\pm 0.03\\left(\\textrm{syst}\\right),\\\ {}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^0\\eta \\right)/\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right)=0.11\\pm 0.01\\left(\\textrm{stat}\\right)\\pm 0.01\\left(\\textrm{syst}\\right),\\\ {}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^0{\\eta}^{\\prime}\\right)/\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right)=0.08\\pm 0.02\\left(\\textrm{stat}\\right)\\pm 0.01\\left(\\textrm{syst}\\right)\\end{array}} $B Ξ c 0 → Ξ 0 π 0 / B Ξ c 0 → Ξ − π + = 0.48 ± 0.02 stat ± 0.03 syst , B Ξ c 0 → Ξ 0 η / B Ξ c 0 → Ξ − π + = 0.11 ± 0.01 stat ± 0.01 syst , B Ξ c 0 → Ξ 0 η ′ / B Ξ c 0 → Ξ − π + = 0.08 ± 0.02 stat ± 0.01 syst for the first time, where the uncertainties are statistical (stat) and systematic (syst). By multiplying by the branching fraction of the normalization mode,$ \\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right) $B Ξ c 0 → Ξ − π + , we obtain the following absolute branching fraction results$ {\\displaystyle \\begin{array}{c}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^0{\\pi}^0\\right)=\\left(6.9\\pm 0.3\\left(\\textrm{stat}\\right)\\pm 0.5\\left(\\textrm{syst}\\right)\\pm 1.3\\left(\\operatorname{norm}\\right)\\right)\\times {10}^{-3},\\\ {}\\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^0\\eta \\right)=\\left(1.6\\pm 0.2\\left(\\textrm{stat}\\right)\\pm 0.2\\left(\\textrm{syst}\\right)\\pm 0.3\\left(\\operatorname{norm}\\right)\\right)\\times {10}^{-3},\\\ {}\\mathcal{B}\\left({\\varXi}_c^0\\to {\\Xi}^0{\\eta}^{\\prime}\\right)=\\left(1.2\\pm 0.3\\left(\\textrm{stat}\\right)\\pm 0.1\\left(\\textrm{syst}\\right)\\pm 0.2\\left(\\operatorname{norm}\\right)\\right)\\times {10}^{-3},\\end{array}} $B Ξ c 0 → Ξ 0 π 0 = 6.9 ± 0.3 stat ± 0.5 syst ± 1.3 norm × 10 − 3 , B Ξ c 0 → Ξ 0 η = 1.6 ± 0.2 stat ± 0.2 syst ± 0.3 norm × 10 − 3 , B Ξ c 0 → Ξ 0 η ′ = 1.2 ± 0.3 stat ± 0.1 syst ± 0.2 norm × 10 − 3 , where the third uncertainties are from$ \\mathcal{B}\\left({\\Xi}_c^0\\to {\\Xi}^{-}{\\pi}^{+}\\right) $B Ξ c 0 → Ξ − π + . The asymmetry parameter for$ {\\Xi}_c^0\\to {\\Xi}^0{\\pi}^0 $Ξ c 0 → Ξ 0 π 0 is measured to be$ \\alpha \\left({\\Xi}_c^0\\to {\\Xi}^0{\\pi}^0\\right)=-0.90\\pm 0.15\\left(\\textrm{stat}\\right)\\pm 0.23\\left(\\textrm{syst}\\right) $α Ξ c 0 → Ξ 0 π 0 = − 0.90 ± 0.15 stat ± 0.23 syst .

We report results from a study ofB^(±) → DK^(±)decays followed byDdecaying toCP eigenstates, whereDindicates aD⁰orD̄⁰meson. 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 of772 × 10⁶ BB̄pairs collected by the Belle experiment and a data set of198 × 10⁶ BB̄pairs collected by the Belle II experiment, both in electron-positron collisions at theΥ(4S)resonance. We measure theCPasymmetries to be 𝓐_(CP +) = (+12.5 ± 5.8 ± 1.4)% and 𝓐_(CP -) = (-16.7 ± 5.7 ± 0.6)% , and the ratios of branching fractions to be 𝓡_(CP+)= 1.164 ± 0.081 ± 0.036 and 𝓡_(CP-) = 1.151 ± 0.074 ± 0.019 . The first contribution to the uncertainties is statistical, and the second is systematic. The asymmetries𝓐_(CP +)and𝓐_(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° ) and0.321

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