Belle II is a new-generation B-factory experiment, dedicated to exploring new physics beyond the standard model of elementary particles in the flavor sector. Belle II started data-taking in April ...2018, using a synchronous data acquisition (DAQ) system based on pipelined trigger flow control. The Belle II DAQ system is designed to handle a 30-kHz trigger rate with approximately 1% of dead time, under the assumption of a raw event size of 1 MB. The DAQ system is reliable, and the overall data-taking efficiency reached 84.2% during the run period of January 2020-June 2020. The current readout system cannot be operated in the terms of ten years from the viewpoint of DAQ maintainability; meanwhile, the readout system is obstructing high-speed data transmission. A solution involving a peripheral component interconnect (PCI)-express-based readout module with high data throughput of up to 100 Gb/s was adopted to upgrade the Belle II DAQ system. We particularly focused on the design of firmware and software based on this new generation of readout board, called PCIe40, with an Altera Arria 10 field-programmable gate array chip. The 48-Gb transceiver (GBT) serial links, PCI-express hard IP-based direct memory access (DMA) architecture, interface of timing and trigger distribution system, and slow control system were designed to integrate with the current Belle II DAQ system. This article describes the performances accomplished during the data readout and slow control tests conducted using a test bench and a demonstration performed using on-site front-end electronics, specifically involving Belle II TOP and KLM subdetectors.
The Belle II experiment and the SuperKEKB collider are designed to operate under a higher luminosity compared to that of Belle for the improvement of rare <inline-formula> <tex-math ...notation="LaTeX">B </tex-math></inline-formula> meson decay study and new physics search. To break the bottleneck of bandwidth and to improve the stability in the operation of the Belle II data acquisition (DAQ) system, a new PCI-express-based readout system has been developed. The new system includes a PCI-express-based high-speed readout board (PCIe40), which was originally developed for the upgrades of the LHCb and ALICE experiments, the PCIe40 firmware, the slow control, and readout software running on a readout PC. The new readout system's commissioning with most of the Belle II subdetectors has been performed, and the readout upgrade is complete for the particle-identification detectors and the neutral kaon and muon detector in Belle II, which has been operating stably with the new system in the beam collision "physics runs." The results of the commissioning and the performance of the global DAQ operation will be reported.
The front-end electronics system for the Belle II Time-Of-Propagation (TOP) counter was fully installed in May 2016. The detector is a novel particle identification device for the barrel region, ...where Cherenkov ring images are reconstructed with precise timing information of each photon. The readout electronics need to have excellent timing performance for single photon detection. To exploit the benefit of high luminosity, the electronics must also be able to cope with a high input trigger rate (30 kHz) and have buffer memory which is deep enough to wait for a trigger decision (>5 μs). The TOP electronics has switching capacitor arrays to sample waveforms with 2.7 GSample/s, which allows a timing resolution of 50 ps for a single photon signal. The programmable logic and the processing system are the effective implementation to meet these requirements, where flexible optimization and step-by-step development of readout logic are possible. The system has been successfully operated in the first accelerator commissioning runs with beam collisions in 2018, where the typical trigger rate was 500Hz. Operation with a 20 kHz trigger rate was also tested.
•Readout electronics for the Belle II Time-Of-Propagation counter was installed.•A single photon is detected with timing resolution better than 100 ps.•The whole system was successfully operated in the physics run.
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
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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.
Measurements of beam backgrounds in SuperKEKB Phase 2 Liptak, Z.; Paladino, A.; Santelj, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2022, Letnik:
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Journal Article
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The high design luminosity of the SuperKEKB electron–positron collider will result in challenging levels of beam-induced backgrounds in the interaction region. Understanding and mitigating these ...backgrounds is critical to the success of the Belle II experiment. We report on the first background measurements performed after roll-in of the Belle II detector, a period known as SuperKEKB Phase 2, utilizing both the BEAST II system of dedicated background detectors and the Belle II detector itself. We also report on first revisions to the background simulation made in response to our findings. Backgrounds measured include contributions from synchrotron radiation, beam-gas, Touschek, and injection backgrounds. At the end of Phase 2, single-beam backgrounds originating from the 4 GeV positron Low Energy Ring (LER) agree reasonably well with simulation, while backgrounds from the 7 GeV electron High Energy Ring (HER) are approximately one order of magnitude higher than simulation. We extrapolate these backgrounds forward and conclude it is safe to install the Belle II vertex detector.
We present the results of the first Dalitz plot analysis of the decay D0 → K−π+η. The analysis is performed on a data set corresponding to an integrated luminosity of 953 fb−1 collected by the ...Belle detector at the asymmetric-energy e+e− KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels K* ( 892 )0η, K−a0 ( 980 )+, K−a2 ( 1320 )+, K* ( 1410 )0η, K* ( 1680 )−π+ and K2* ( 1980 )−π+, together with Kπ and Kη S-wave components. The decays K* ( 1680 )− → K−η and K2* ( 1980 )− → K−η are observed for the first time. We measure ratio of the branching fractions, ... (B PDG). Using the Dalitz fit result, the ratio ... is measured to be ...; this is much lower than the theoretical expectations ( ≈ 1 ) made under the assumption that K*( 1680 ) is a pure 13D1 state. The product branching fraction ... is determined. In addition, the π η ′ contribution to the a0( 980 )± resonance shape is confirmed with 10.1 σ statistical significance using the three-channel Flatté model. We also measure ... . This is consistent with, and more precise than, the current world average ( 1.02 ± 0.30 ) % , deviates with a significance of more than 3 σ from the theoretical predictions of (0.51–0.92)%. (ProQuest: ... denotes formulae omited.).
To improve the data throughput of the Belle II data acquisition (DAQ), we are upgrading the central processing unit (CPU)-based COPPER system with a PCIe40 board carrying an Arria 10 ...field-programmable gate array (FPGA). Since one of the main functionalities of the new system is event building in the FPGA, the read-out system must be synchronized with the front-end electronics. This task is performed by the bidirectional trigger timing distribution system. During system commissioning, we prepared several versions of the interface to this system. In the initial version of the interface, we ported the code from Xilinx FPGAs to Arria 10. This revision also introduces monitoring of the status for multiple channels and a ring buffer to distribute trigger information to all channels in parallel. To improve stability under external noise, we implemented a clock-data recovery (CDR) using an independent onboard oscillator as a reference clock in the next revision of the interface. We are also developing a version utilizing a high-speed serial transceiver to replace CAT-7 RJ45 cables with optical fibers. The system commissioning started in 2021 with a few detectors and will be completed after the long shutdown 1 of SuperKEKB in 2023. In this article, we present the architectures of the interface to the trigger timing system implemented in the PCIe40 board and the system performance in the experiment.
This work reports the first observation of azimuthal asymmetries around the thrust axis in e+e− annihilation of pairs of back-to-back charged pions in one hemisphere, and π0 and η mesons in the ...opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The π0 and η asymmetries rise with the relative momentum z of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function H1⊥ and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the η final states will provide additional information on the flavor structure of H1⊥. This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4 fb−1 collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV.
We present an analysis of the exclusive B+ → π+ π− ℓ+ νℓ decay, where ℓ represents an electron or a muon, with the assumption of charge-conjugation symmetry and lepton universality. The study ...exploits the full Υ ( 4 S ) data sample collected by the Belle detector, corresponding to 711 fb−1 of integrated luminosity. Events are selected by fully reconstructing one B meson in hadronic decay modes, subsequently determining the properties of the other B meson. We extract the signal yields using a binned maximum-likelihood fit to the missing-mass squared distribution in bins of the invariant mass of the two pions or the momentum transfer squared. We measure a total branching fraction of B(B+ → π+ π− ℓ+ νℓ) = 22.7+1.9 −1.6 (stat) ± 3.5(syst) × 10−5, where the uncertainties are statistical and systematic, respectively. This result is the first reported measurement of this decay.
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