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A bstract We present a measurement of the time-dependent CP asymmetry in decays using a data set of 365 fb − 1 recorded by the Belle II experiment and the final data set of 711 fb − 1 recorded by the Belle experiment at the Υ(4S) resonance. The direct and mixing-induced time-dependent CP violation parameters C and S are determined along with two additional quantities, S + and S − , defined in the two halves of the plane. The measured values are C = − 0 . 17 ± 0 . 09 ± 0 . 04, S = − 0 . 29 ± 0 . 11 ± 0 . 05, S + = −0 . 57 ± 0 . 23 ± 0 . 10 and S − = 0 . 31 ± 0 . 24 ± 0 . 05, where the first uncertainty is statistical and the second systematic.

We present a measurement of the time-dependent CP asymmetry in$${B}^{0}\\to {K}_{\\text{S}}^{0}{\\pi }^{+}{\\pi }^{-}\\gamma $$decays using a data set of 365 fb − 1 recorded by the Belle II experiment and the final data set of 711 fb − 1 recorded by the Belle experiment at the Υ(4S) resonance. The direct and mixing-induced time-dependent CP violation parameters C and S are determined along with two additional quantities, S + and S − , defined in the two halves of the$${m}^{2}\\left({K}_{\\text{S}}^{0}{\\pi }^{+}\\right)-{m}^{2}\\left({K}_{\\text{S}}^{0}{\\pi }^{-}\\right)$$plane. The measured values are C = − 0 . 17 ± 0 . 09 ± 0 . 04, S = − 0 . 29 ± 0 . 11 ± 0 . 05, S + = −0 . 57 ± 0 . 23 ± 0 . 10 and S − = 0 . 31 ± 0 . 24 ± 0 . 05, where the first uncertainty is statistical and the second systematic.

We present a measurement of the time-dependent CP asymmetry in decays using a data set of 365 fb−1 recorded by the Belle II experiment and the final data set of 711 fb−1 recorded by the Belle experiment at the Υ(4S) resonance. The direct and mixing-induced time-dependent CP violation parameters C and S are determined along with two additional quantities, S+ and S−, defined in the two halves of the plane. The measured values are C = −0.17 ± 0.09 ± 0.04, S = −0.29 ± 0.11 ± 0.05, S+ = −0.57 ± 0.23 ± 0.10 and S− = 0.31 ± 0.24 ± 0.05, where the first uncertainty is statistical and the second systematic.

We search for the \\(e^+ e^- \\to \\gamma \\chi_{bJ}\\) (\\(J\\) = 0, 1, 2) processes at center-of-mass energies \\(\\sqrt{s}\\) = 10.653, 10.701, 10.746, and 10.804 GeV. These data were collected with the Belle II detector at the SuperKEKB collider and correspond to 3.5, 1.6, 9.8, and 4.7 fb\\(^{-1}\\) of integrated luminosity, respectively. We set upper limits at the 90\\% confidence level on the Born cross sections for \\(e^+ e^- \\to \\gamma \\chi_{bJ}\\) at each center-of-mass energy \\(\\sqrt{s}\\) near 10.746 GeV. The upper limits at 90\\% confidence level on the Born cross sections for \\(e^+ e^- \\to \\gamma \\chi_{b1}\\) are significantly smaller than the corresponding measured values for \\(e^+e^-\\to\\omega\\chi_{b1}\\) and \\(e^+e^-\\to\\pi^+\\pi^-\\Upsilon(2S)\\) at \\(\\sqrt{s}\\) = 10.746 GeV.

A sample of 365 fb\\(^{-1}\\) of \\(e^+e^- \\to \\Upsilon(4S) \\to B\\bar{B}\\) data collected by the Belle II experiment is used to measure the partial branching fractions of charmless semileptonic \\(B\\) meson decays and determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element \\(V_{ub}\\). Events containing a signal electron or muon \\(\\ell\\) and a fully reconstructed hadronic \\(B\\) decay that constrains the signal kinematics are selected, while the rest of the event defines the hadronic system \\(X_u\\) associated with the signal. To discriminate the signal from the 50-times larger background originating from CKM-favored semileptonic \\(B\\) decays, a template fit is performed in both signal and control regions after applying an optimized selection. The partial branching fraction measured for lepton energies greater than 1 GeV in the signal \\(B\\) meson rest frame is \\(\\Delta\\mathcal{B}(B \\to X_u \\ell \\nu) = (1.54 \\pm 0.08 \\, {\\rm (stat.)} \\pm 0.12 \\, {\\rm (syst.)}) \\times 10^{-3}\\). From this measurement, using the Gambino, Giordano, Ossola, Uraltsev theoretical framework, \\(|V_{ub}| = (4.01 \\pm 0.19 ^{+0.07} _{-0.08}) \\times 10^{-3}\\) is determined, where the uncertainties are experimental and theoretical, respectively. This value is consistent with the world average obtained from previous inclusive measurements. Different theoretical predictions and partial branching fractions measured in other phase-space regions, defined by additional selections on the \\(X_u\\) and leptonic system masses, are also used to determine \\(|V_{ub}|\\).

We report a search for the rare decay \\(B^{+} \\rightarrow K^{+} \\tau^{+} \\tau^{-}\\) using \\(1.2 \\times 10^9\\) \\(\\Upsilon(4S)\\) mesons produced near threshold in electron-positron collisions and collected by the Belle and Belle~II experiments. We fully reconstruct the hadronic decay of one \\(B\\) meson produced in the \\(\\Upsilon(4S)\\rightarrow B^{+} B^{-}\\) decay, and search for \\(B^{\\pm}\\rightarrow K^{\\pm} \\tau^{+}\\tau^{-}\\) candidates among the remaining collision products, reconstructing a charged kaon and leptonic decays of the \\(\\tau\\) leptons. We optimize the selection for best sensitivity and look for an excess over background at low values of the residual energy detected in the calorimeter after full event reconstruction. We observe no significant excess and set the limit \\(\\mathcal{B}(B^{+}\\rightarrow K^{+}\\tau^{+}\\tau^{-})< 0.56\\times 10^{-3}\\) at the 90% confidence level, improving on the only previous result by a factor of four.

The silicon strip sensors of the Belle II silicon vertex detector were irradiated with 90 MeV electron beams up to an equivalent 1-MeV-neutron fluence of \\(3.0\\times 10^{13}~{\\rm n}_{\\rm eq}/{\\rm cm^2}\\). We measure changes in sensor properties induced by radiation damage in the semiconductor bulk. Electrons around this energy are a major source of beam-induced background during Belle II operation. We discuss observed changes in full depletion voltage, sensor leakage current, noise, and charge collection. The sensor bulk type inverts at an equivalent 1-MeV-neutron fluence of \\(6.0\\times 10^{12}~{\\rm n}_{\\rm eq}/{\\rm cm^2}\\). The leakage current increases proportionally to the radiation dose. We determine a damage constant of \\(3.9 \\times 10^{-17}\\) A/cm at 17 C\\(^\\circ\\) immediately after irradiation, which drops significantly to approximately 40% of the initial value in 200 hours, then stabilizes to approximately 30% of the initial value in 1000 hours. We measure sensor noise and signal charge for a sensor irradiated with the equivalent 1-MeV-neutron fluence of \\(3.0\\times 10^{13}~{\\rm n}_{\\rm eq}/{\\rm cm^2}\\). Noise increases by approximately 44% after irradiation, while signal charge does not change significantly when a sufficiently high bias voltage is applied.

Using a data sample of 427.9 fb\\(^-1\\) collected by the Belle~II detector at or near the \\((4S)\\) and \\((10753)\\) resonances, the cross sections for \\(e^+e^- h^+h^-J/\\) \\((h=/K/p)\\) at center-of-mass energies ranging from 3.8 GeV or the production threshold to 5.5/6.0/7.0 GeV have been measured via initial-state radiation. The cross sections for the processes \\(e^+e^- ^+^-J/\\) and \\(e^+e^- K^+K^-J/\\) are consistent with previously published results. The cross sections for these channels obtained by combining with previous Belle results are also given. The process \\(e^+e^- p p J/\\) is investigated for the first time. The yields are small and no significant structure is observed in the cross section versus energy. Searches for vector charmonium-like states in the \\(h^+h^-J/\\) systems, and for associated intermediate states in the \\(h^ J/\\) systems, are also presented.

We measure the time- and phase-space-integrated \\(CP\\) asymmetry \\(A_{CP}\\) in \\(D^0\\to\\pi^+\\pi^-\\pi^0\\) decays reconstructed in \\(e^+e^-\\to c\\bar c\\) events collected by the Belle II experiment from 2019 to 2022. This sample corresponds to an integrated luminosity of 428 fb\\(^{-1}\\). We require \\(D^0\\) mesons to be produced in \\(D^{*+}\\to D^0\\pi^+\\) decays to determine their flavor at production. Control samples of \\(D^0\\to K^-\\pi^+\\) decays are used to correct for reconstruction-induced asymmetries. The result, \\(A_{CP}(D^0\\to\\pi^+\\pi^-\\pi^0)=(0.29\\pm0.27\\pm0.13)\\%\\), where the first uncertainty is statistical and the second systematic, is the most precise result to date and is consistent with \\(CP\\) conservation.

Using data samples of 988.4 fb\\(^{-1}\\) and 427.9 fb\\(^{-1}\\) collected with the Belle and Belle II detectors, we present a study of the singly Cabibbo-suppressed decays \\(\\Xi_c^{0} \\to \\Lambda \\eta\\), \\(\\Lambda \\eta'\\), and \\(\\Lambda \\pi^0\\). We observe the decay \\(\\Xi_c^0 \\to \\Lambda \\eta\\) and find evidence for the decay \\(\\Xi_c^0 \\to \\Lambda \\eta'\\), with corresponding branching ratios determined to be \\({\\mathcal{B}(\\Xi_c^0 \\to \\Lambda \\eta)}/{\\mathcal{B}(\\Xi_c^0 \\to \\Xi^- \\pi^+)}= (4.16 \\pm 0.91 \\pm {0.23})\\%\\) and \\({\\mathcal{B}(\\Xi_c^0 \\to \\Lambda \\eta')}/{\\mathcal{B}(\\Xi_c^0 \\to \\Xi^- \\pi^+)}= (2.48 \\pm 0.82 \\pm {0.12})\\%\\), respectively. We find no significant signal in the \\(\\Xi_c^0 \\to \\Lambda \\pi^0\\) decay mode and set an upper limit at the 90% credibility level of \\({\\mathcal{B}(\\Xi_c^0 \\to \\Lambda \\pi^0)}/{\\mathcal{B}(\\Xi_c^0 \\to \\Xi^- \\pi^+)}< {3.5\\%}\\). Multiplying these ratios by the world-average branching fraction of the normalization channel, \\(\\mathcal{B}(\\Xi_c^0 \\to \\Xi^- \\pi^+)=(1.43 \\pm 0.27)\\%\\), we obtain the absolute branching fractions of \\(\\mathcal{B}(\\Xi_c^0 \\to \\Lambda \\eta)= (5.95 \\pm 1.30 \\pm {0.32} \\pm 1.13) \\times 10^{-4}\\), \\(\\mathcal{B}(\\Xi_c^0 \\to \\Lambda \\eta')= (3.55 \\pm 1.17 \\pm {0.17} \\pm 0.68) \\times 10^{-4}\\), and an upper limit at the 90% credibility level on the absolute branching fraction of \\(\\mathcal{B}(\\Xi_c^0 \\to \\Lambda \\pi^0)< {5.2} \\times 10^{-4}\\). The quoted first and second uncertainties are statistical and systematic, respectively, while the third uncertainties arise from the branching fraction of the normalization mode. These results are consistent with most theoretical predictions and further the understanding of the underlying decay mechanisms.