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The Belle II experiment is a new generation B-factory experiment at KEK in Japan aiming at the search for New Physics in a huge sample of B-meson decays. The commissioning of the accelerator and the detector for the first physics run has started from March this year. The Belle II High Level Trigger (HLT) is fully working in the beam run. The HLT is now operated with 1600 cores clusterized in 5 units, which is 1/4 of the full configuration. The software trigger is performed using the same o ffl ine reconstruction code, and events are classified into a set of physics categories. Only the events in the categories of interest are finally sent out to the storage. Live data quality monitoring is also performed on HLT. For the selected events, the reconstructed tracks are extrapolated to the surface of the pixel detector (PXD) and quickly fed back to the readout electronics for the real time data reduction by sending only the associated hits. The maximum trigger rate in the first physics run was 3.5kHz, and the Belle II data acquisition system was stably operated. There were several problems in the HLT operation, but they have successfully been fixed during the data taking period. The HLT reduction factor is measured to be 8 which is still higher than the design because of the high background environment.

We show two different absolute distance measurement methods with micrometer accuracy based on frequency combs, and we discuss possible applications. Using a mode- locked laser and MEMS-based tracking optics, we measure the 3D position of a retroreflector within 10 ms and with a 24 μm volumetric accuracy. We also investigate modulator-based combs and show that they enable highly sensitive surface topography measurements with microsecond acquisition times and micrometer precision. Moreover, the potential for photonic integration of frequency comb sources is explored.

Abstract 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 −1 data sample collected at the Υ(10860) resonance by the Belle detector at the KEKB asymmetric-energy e + 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$${D}_{s}^{+}$$, D 0, and D + 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$${f}_{s}=\\left({21.4}_{-1.7}^{+1.5}\\right)\\%$$.

Abstract We report measurements of the e + e − → B B ¯ BB̅ , B B ¯ ∗ BB̅^(∗) , and B ∗ B ¯ ∗ B^(∗)B̅^(∗) cross sections at four energies, 10653, 10701, 10746 and 10805 MeV, using data collected by the Belle II experiment. We reconstruct one B meson in a large number of hadronic final states and use its momentum to identify the production process. In the first 2 – 5 MeV above B ∗ B ¯ ∗ B^(∗)B̅^(∗) threshold, the e + e − → B ∗ B ¯ ∗ B^(∗)B̅^(∗) cross section increases rapidly. This may indicate the presence of a pole close to the threshold.

Abstract 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 D̅⁰ mesons, in a likelihood fit to obtain ϕ 3 = (75.2 ± 7.6) ° . We also briefly discuss the interpretation of this result.

Abstract We present measurements of the branching fractions of eight B ¯ 0$$ {\\overline{B}}^0 $$→ D (*)+ K − K S ∗ 0$$ {K}_{(S)}^{\\left(\\ast \\right)0} $$, B − → D (*)0 K − K S ∗ 0$$ {K}_{(S)}^{\\left(\\ast \\right)0} $$decay channels. The results are based on data from SuperKEKB electron-positron collisions at the Υ(4S) 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$$ {K}_{(S)}^{\\left(\\ast \\right)0} $$) and m(D (*) K S ∗ 0$$ {K}_{(S)}^{\\left(\\ast \\right)0} $$) in order to avoid dependence on the decay model. These results include the first observation of B ¯ 0$$ {\\overline{B}}^0 $$→ D + K − K S 0$$ {K}_S^0 $$, B − → D* 0 K − K S 0$$ {K}_S^0 $$, and B ¯ 0$$ {\\overline{B}}^0 $$→ D* + K − K S 0$$ {K}_S^0 $$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$$ {K}_{(S)}^{\\left(\\ast \\right)0} $$systems are compatible with quasi-two-body decays via a resonant transition with spin-parity J P = 1− for the K − K S 0$$ {K}_S^0 $$systems and J P = 1+ for the K − K* 0 systems. We also present measurements of the branching fractions of four B ¯ 0$$ {\\overline{B}}^0 $$→ D (*)+ D s −$$ {D}_s^{-} $$, B − → D (*)0 D s −$$ {D}_s^{-} $$decay channels with a precision compatible to the current world averages.

Abstract We report results from a study of B ± → DK ± decays followed by D decaying to the CP-even final state K + K − and CP-odd final state K S 0 π 0 K_(S)⁰π⁰ , where D is an admixture of D 0 and D ¯ 0 D̅⁰ states. These decays are sensitive to the Cabibbo-Kobayashi-Maskawa unitarity-triangle angle ϕ 3. The results are based on a combined analysis of the final data set of 772 × 106 B B ¯ BB̅ pairs collected by the Belle experiment and a data set of 198 × 106 B B ¯ BB̅ pairs collected by the Belle II experiment, both in electron-positron collisions at the Υ(4S) resonance. We measure the CP asymmetries to be A 𝓐 CP+ = (+12.5 ± 5.8 ± 1.4)% and A 𝓐 CP− = (−16.7 ± 5.7 ± 0.6)%, and the ratios of branching fractions to be R 𝓡 CP+ = 1.164 ± 0.081 ± 0.036 and R 𝓡 CP− = 1.151 ± 0.074 ± 0.019. The first contribution to the uncertainties is statistical, and the second is systematic. The asymmetries A 𝓐 CP+ and 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 ° < ϕ 3 < 16.5 ° ) or (84.5 ° < ϕ 3 < 95.5 ° ) or (163.3 ° < ϕ 3 < 171.5 ° ) and 0.321 < r B < 0.465.

Abstract We measure CP asymmetries and branching-fraction ratios for B ± → DK ± and Dπ ± decays with D → K S 0$$ {K}_{\\textrm{S}}^0 $$K ± π ∓, where D is a superposition of D 0 and D ¯$$ \\overline{D} $$0. We use the full data set of the Belle experiment, containing 772 × 106 B B ¯$$ B\\overline{B} $$pairs, and data from the Belle II experiment, containing 387 × 106 B B ¯$$ B\\overline{B} $$pairs, both collected in electron-positron collisions at the Υ(4S) resonance. Our results provide model-independent information on the unitarity triangle angle ϕ 3.

HADES is a secondary generation experiment operated at GSI Darmstadt with the main goal to study dielectron production in proton, pion and heavy ion induced reactions. The first part of the HADES mission is to reinvestigate the puzzling pair excess measured by the DLS collaboration in C + C and Ca + Ca collisions at 1  A  GeV. For this purpose dedicated measurements with the C + C system at 1 and 2  A  GeV were performed. The pair excess above a cocktail of free hadronic decays has been extracted and compared to the one measured by DLS. Furthermore, the excess is confronted with predictions of various model calculations.

The results of a full simulation of an endcap Time-of-Flight detector upgrade based on multigap resistive plate chambers for the BESIII experiment are presented. The simulation and reconstruction software is based on Geant4 and has been implemented into the BESIII Offline Software System. The results of the simulations are compared with beam test results and it is shown that a total time resolution \\(\\sigma\\) of about 80 ps can be achieved allowing for a pion and kaon separation up to momenta of 1.4 GeV/c at a 95% confidence level.