arXiv subjects

Satoru Yamada

Publications and source records attributed to Satoru Yamada.

4 recordsLinked to original sources

arXiv2026

Migration of Belle II TOP Feature Extraction from the Zynq Processing System to PCIe40 Readout PCs

The Belle II Time-of-Propagation (TOP) detector is a key system for charged-particle identification (PID). Although TOP operated successfully during initial Belle II data taking, increasing luminosity and beam-induced background led to more frequent single-event upsets (SEUs) in the radiation-exposed Zynq systems-on-chip (SoCs). Resulting lockups of the embedded processing systems (PSs) interrupted data acquisition. To mitigate this limitation, waveform feature extraction, a critical task of the on-detector Zynq PS, was migrated to the off-detector PCIe40 readout PCs (ROPCs). The new architecture bypasses the PS in the event data path and performs feature extraction outside the detector radiation environment. This change removed SEU-induced PS lockups from the event data path and enabled stable operation of the TOP front-end electronics and the Belle II data-acquisition system under increased luminosity and background conditions. The typical TOP deadtime decreased from about 1% to a level consistent with zero after the final firmware patch, and stable operation was demonstrated at a Level-1 (L1) trigger rate of 30 kHz with a microchannel-plate photomultiplier-tube (MCP-PMT) hit rate of approximately 5 MHz per PMT. This paper describes the migrated architecture, its deployment and validation, and its operational and PID performance.

physics.ins-det↗

arXiv2025

Velocity dependence of the mass modifications of $ρ$ and $ω$ mesons in 12 GeV $p+A$ reactions

This study measured the invariant mass spectra of $ρ$ and $ω$ mesons in the $e^+e^-$ decay channel for 12 GeV (12.9 GeV/$c$) $p+\mathrm{C}$ and $p+\mathrm{Cu}$ reactions ($\sqrt{s}_{NN}=5.1$ GeV) at the KEK 12-GeV Proton Synchrotron. The measured spectra were divided into three $βγ$ regions to examine their velocity dependence. Across all regions, significant excesses were observed on the low-mass side of the $ω$ meson peak, beyond the contributions of known hadronic sources, in the data of the C and Cu targets. Model calculations were subsequently performed to evaluate the magnitudes of the mass modifications of $ρ$ and $ω$ mesons.

nucl-ex↗

arXiv2025

Analysis of spectral modification of $\phi$ mesons at finite density using a transport approach in the 12 GeV pA reactions

The hadron spectrum at finite density is an important observable for exploring the origin of hadron masses. In the KEK-PS E325 experiment, the di-electron decays of phi mesons inside and outside nuclei were measured using 12 GeV pA reactions. In the previous analysis, a significant excess was observed on the low-mass side of the phi meson peak in the data for slow-moving phi mesons ($\beta\gamma=p_{\phi}/m_{\phi}<1.25$) with the Cu target, and in-medium vector meson spectral modification was verified. We newly employed the PHSD transport approach to take into account the time evolution of spatial density distribution of the target nuclei. Consistent with the previous analysis, a significant excess was observed in the present analysis as well. It was found that incorporating momentum dependence into the spectral modification leads to better agreement with the experimental results. For the slow-moving $\phi$ mesons with the Cu target, the newly obtained modification parameters are consistent with those from the previous analysis within the uncertainties.

nucl-ex↗

arXiv2021

Performance of the Unified Readout System of Belle II

The Belle II experiment at the SuperKEKB collider at KEK, Tsukuba, Japan has successfully started taking data with the full detector in March 2019. Belle II is a luminosity frontier experiment of the new generation to search for physics beyond the Standard Model of elementary particles, from precision measurements of a huge number of B and charm mesons and tau leptons. In order to read out the events at a high rate from the seven subdetectors of Belle II, we adopt a highly unified readout system, including a unified trigger timing distribution system (TTD), a unified high speed data link system (Belle2link), and a common backend system to receive Belle2link data. Each subdetector frontend readout system has a field-programmable gate array (FPGA) in which unified firmware components of the TTD receiver and Belle2link transmitter are embedded. The system is designed for data taking at a trigger rate up to 30 kHz with a dead-time fraction of about 1% in the frontend readout system. The trigger rate is still much lower than our design. However, the background level is already high due to the initial vacuum condition and other accelerator parameters, and it is the most limiting factor of the accelerator and detector operation. Hence the occupancy and radiation effects to the frontend electronics are rather severe, and they cause various kind of instabilities. We present the performance of the system, including the achieved trigger rate, dead-time fraction, stability, and discuss the experience gained during the operation.

physics.ins-det↗