Explore the vast range of titles available.

We present the study of an end-to-end multi-track reconstruction algorithm for the central drift chamber of the Belle II experiment at the SuperKEKB collider using Graph Neural Networks for an unknown number of particles. The algorithm uses detector hits as inputs without pre-filtering to simultaneously predict the number of track candidates in an event and their kinematic properties. In a second step, we cluster detector hits for each track candidate to pass to a track fitting algorithm. Using a realistic full detector simulation including beam-induced backgrounds and detector noise taken from actual collision data, we find significant improvements in track finding efficiencies for tracks in a variety of different event topologies compared to the existing baseline algorithm used in Belle II. For events involving a hypothetical long-lived massive particle with a mass in the GeV-range, decaying uniformly along its flight direction into two charged particles, the GNN achieves a combined track finding and fitting charge efficiency of 85.4% per track, with a fake rate of 2.5%, averaged over the full detector acceptance. In comparison, the baseline algorithm achieves 52.2% efficiency and a fake rate of 4.1%. This is the first end-to-end multi-track machine learning algorithm for a drift chamber detector that has been utilized in a realistic particle physics environment.

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_{\\rm 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 \\({\\rm \\Upsilon(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(K_{\\rm S}^0 \\pi^{+})-m^2(K_{\\rm S}^0 \\pi^{-})\\) plane. The measured values are \\(C = -0.17 \\pm 0.09 \\pm 0.04\\), \\(S = -0.29 \\pm 0.11 \\pm 0.05\\), \\(S^{+} = -0.57 \\pm 0.23 \\pm 0.10\\) and \\(S^{-} = 0.31 \\pm 0.24 \\pm 0.05\\), where the first uncertainty is statistical and the second systematic.

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.

We recently measured the branching fraction of the \\(B^{+}\\rightarrow K^{+}\\nu\\bar{\\nu}\\) decay using 362fb\\(^{-1}\\) of on-resonance \\(e^+e^-\\) collision data under the assumption of Standard Model kinematics, providing the first evidence for this decay. To facilitate future reinterpretations and maximize the scientific impact of this measurement, we publicly release the full analysis likelihood along with all necessary material required for reinterpretation under arbitrary theoretical models sensitive to this measurement. In this work, we demonstrate how the measurement can be reinterpreted within the framework of the Weak Effective Theory. Using a kinematic reweighting technique in combination with the published likelihood, we derive marginal posterior distributions for the Wilson coefficients, construct credible intervals, and assess the goodness of fit to the Belle II data. For the Weak Effective Theory Wilson coefficients, the posterior mode of the magnitudes \\(|C_\\mathrm{VL}+C_\\mathrm{VR}|\\), \\(|C_\\mathrm{SL}+C_\\mathrm{SR}|\\), and \\(|C_\\mathrm{TL}|\\) corresponds to the point \\({(11.3, 0.0, 8.2)}\\). The respective 95\\% credible intervals are \\([1.9, 16.2]\\), \\([0.0, 15.4]\\), and \\([0.0, 11.2]\\).

We report decay-rate \\(CP\\) asymmetries of the singly-Cabibbo-suppressed decays \\(_c^+^+h^+h^-\\) and \\(_c^+ ph^+h^-\\), with \\(h=K,\\), measured using 428 fb\\(^-1\\) of \\(e^+e^-\\) collisions collected by the Belle II experiment at the SuperKEKB collider. The results, equation A_CP(_c^+^+K^+K^-) = (3.76.60.6)\\%, equation equation A_CP(_c^+^+^+^-) = (9.56.80.5)\\%, equation equation A_CP(_c^+ pK^+K^-) = (3.91.70.7)\\%, equation equation A_CP(_c^+ p^+^-) = (0.31.00.2)\\%, equation where the first uncertainties are statistical and the second systematic, agree with \\(CP\\) symmetry. From these results we derive the sums equation A_CP(_c^+^+^+^-) \\, + \\, A_CP(_c^+ pK^+K^-) = (13.4 7.0 0.9)\\%, equation equation A_CP(_c^+^+K^+K^-) \\, + \\, A_CP(_c^+ p^+^-) = (04.0 6.6 0.7)\\%, equation which are consistent with the \\(U\\)-spin symmetry prediction of zero. These are the first measurements of \\(CP\\) asymmetries for individual hadronic three-body charmed-baryon decays.

We measure the time-integrated CP asymmetry in \\(D^{0} \\rightarrow K^{0}_{S}K^{0}_{S}\\) decays reconstructed in \\(e^{+}e^{-} \\rightarrow c\\overline{c}\\) events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 fb\\(^{-1}\\) and 428 fb\\(^{-1}\\), respectively. The \\(D^{0}\\) decays are required to originate from the \\(D^{*+} \\rightarrow D^{0}\\pi^{+}\\) decay, which determines the charm flavor at production time. A control sample of \\(D^{0} \\rightarrow K^{+}K^{-}\\) decays is used to correct for production and detection asymmetries. The result, \\((-1.4\\pm1.3{\\rm(stat)}\\pm0.1{\\rm (syst)})\\%\\), is consistent with previous determinations and with CP symmetry.

We measure the time-integrated \\(CP\\) asymmetry in \\(D^0 K^0_ S K^0_ S\\) decays reconstructed in \\(e^+e^- c c\\) events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 and 428 fb\\(^-1\\), respectively. To infer the flavor of the \\(D^0\\) meson, we exploit the correlation between the flavor of the reconstructed decay and the electric charges of particles reconstructed in the rest of the \\(e^+e^- c c\\) event. This results in a sample which is independent from any other previously used at Belle or Belle II. The result, \\(A_CP(D^0 K^0_ S K^0_ S) = (1.3 2.0 0.2)\\%\\), where the first uncertainty is statistical and the second systematic, is consistent with previous determinations and with \\(CP\\) symmetry.

We present the results of a search for the charged-lepton-flavor violating decays \\(B^0 K^*0^ ^\\), where \\(^\\) is either an electron or a muon. The results are based on 365 fb\\(^-1\\) and 711 fb\\(^-1\\) datasets 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^ ^\\) decays and set upper limits on the branching fractions in the range of \\((2.9-6.4)10^-5\\) at 90% confidence level.

We observe the radiative decay \\(D^{*}_{s0}(2317)^{+} \\to D_{s}^{*+} \\gamma\\) for the first time, with a significance exceeding \\(10\\) standard deviations. The signal is found in the continuum \\(e^+ e^- \\to c\\bar{c}\\) process with the combined data samples of 980.4~\\(\\rm fb^{-1}\\) and 427.9~\\(\\rm fb^{-1}\\) collected by the Belle and Belle~II detectors operating at the KEKB and SuperKEKB asymmetric-energy \\(e^+e^-\\) colliders, respectively. The branching fraction ratio \\({\\cal B}(D^{*}_{s0}(2317)^{+} \\to D_{s}^{*+} \\gamma)/{\\cal B}(D^{*}_{s0}(2317)^{+} \\to D_{s}^{+} \\pi^{0})\\) is measured to be \\([7.14 \\pm 0.70({\\rm stat.}) \\pm 0.23({\\rm syst.})]\\%\\). This result provides significant new experimental input for the determination of the quark structure of the \\(D^{*}_{s0}(2317)^{+}\\), which remains unknown.