Explore the vast range of titles available.

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 of the branching fractions of eight B ¯ 0 → D (*)+ K − K S ∗ 0 , B − → D (*)0 K − K S ∗ 0 decay channels. The results are based on data from SuperKEKB electron-positron collisions at the Υ(4 S ) resonance collected with the Belle II detector, corresponding to an integrated luminosity of 362 fb − 1 . The event yields are extracted from fits to the distributions of the difference between expected and observed B meson energy, and are efficiency-corrected as a function of m ( K − K S ∗ 0 ) and m ( D (*) K S ∗ 0 ) in order to avoid dependence on the decay model. These results include the first observation of B ¯ 0 → D + K − K S 0 , B − → D* 0 K − K S 0 , and B ¯ 0 → D* + K − K S 0 decays and a significant improvement in the precision of the other channels compared to previous measurements. The helicity-angle distributions and the invariant mass distributions of the K − K S ∗ 0 systems are compatible with quasi-two-body decays via a resonant transition with spin-parity J P = 1 − for the K − K S 0 systems and J P = 1 + for the K − K* 0 systems. We also present measurements of the branching fractions of four B ¯ 0 → D (*)+ D s − , B − → D (*)0 D s − decay channels with a precision compatible to the current world averages.

A bstract We measure CP asymmetries and branching-fraction ratios for B ± → DK ± and Dπ ± decays with D → K S 0 K ± π ∓ , where D is a superposition of D 0 and D ¯ 0 . We use the full data set of the Belle experiment, containing 772 × 10 6 B B ¯ pairs, and data from the Belle II experiment, containing 387 × 10 6 B B ¯ pairs, both collected in electron-positron collisions at the Υ(4 S ) resonance. Our results provide model-independent information on the unitarity triangle angle ϕ 3 .

A bstract We report a determination of the CKM angle ϕ 3 , also known as γ , from a combination of measurements using samples of up to 711 fb − 1 from the Belle experiment and up to 362 fb − 1 from the Belle II experiment. We combine results from analyses of B + → DK + , B + → Dπ + , and B + → D * K + decays, where D is an admixture of D 0 and D ¯ 0 mesons, in a likelihood fit to obtain ϕ 3 = (75.2 ± 7.6) ° . We also briefly discuss the interpretation of this result.

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))% .

A bstract We report measurements of the absolute branching fractions , , and , where the latter is measured for the first time. The results are based on a 121.4 fb − 1 data sample collected at the Υ(10860) resonance by the Belle detector at the KEKB asymmetric-energy e + e − collider. We reconstruct one meson in events and measure yields of , D 0 , and D + mesons in the rest of the event. We obtain , , and , where the first uncertainty is statistical and the second is systematic. Averaging with previous Belle measurements gives and . For the production fraction at the Υ(10860), we find .

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 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

Journal Article

Share this book

Add to My Shelf