arXiv subjects

Keisuke Yoshihara

Publications and source records attributed to Keisuke Yoshihara.

9 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↗

arXiv2026

Machine-Learning-Based Waveform Discrimination in the Front-End Electronics of the Belle II Central Drift Chamber for Cross-Talk Noise Reduction

Machine learning (ML) inference on FPGAs has been widely adopted in real-time triggering of collider experiments for detector signature identification. In contrast, the ML application in Front-End Electronics (FEE) has not yet been fully explored, primarily due to constraints such as limited FPGA resources, power consumption, and localized detector coverage. In this work, we develop an ML-based waveform discrimination method for the Central Drift Chamber (CDC) of the Belle II experiment to suppress cross-talk noise at the front-end level. The Belle II CDC is a key charged-particle tracking detector for both offline and the real-time hardware trigger. During Belle II operation, background wire hits have been observed in the CDC FEE, where multiple hits occur in neighboring anode wires by large energy deposit. The hardware track trigger employs a Hough transformation based on track segments formed by combining hits from multiple wire layers. Due to the reduced information, the track trigger is sensitive to cross-talk noise, hence resulting in an increased fake trigger rate with higher luminosity in the future. We employ compact and fast Boosted Decision Tree models implemented in a Xilinx Virtex-5 FPGA of the CDC FEE, where waveform is processed independently for each wire channel in a fully pipelined manner. Offline studies show that the cross-talk noise can be reduced by approximately a factor of two while maintaining a signal efficiency above 98%. The firmware validation during dedicated Belle II calibration runs demonstrated reductions of up to 50% in track segment and trigger rates while preserving the trigger acceptance for events containing tracks within 10%. This work demonstrates the technical feasibility of compact and low-latency ML inference in detector FEE and highlights its potential for future intelligent detector readout systems in high-energy physics experiments.

physics.ins-det↗

arXiv2026

Development of a Silicon-Based Ultra-Fast X-Ray Beam Size Monitor for SuperKEKB

We present the development of a silicon-based ultra-fast X-ray beam size monitor (SiXRM) for SuperKEKB. The system enables, for the first time at SuperKEKB, bunch-by-bunch measurements of the vertical beam size using synchrotron radiation. The detector combines a silicon strip sensor board, amplifier boards, and fast waveform readout electronics. Beam measurements demonstrate clear reconstruction of the bunch structure and X-ray images for individual bunches. The measured beam sizes show good agreement with those obtained from the existing CMOS-based XRM system. The measurement precision is estimated to be better than 6.4 $\mu$m. This system provides a powerful tool for studying beam dynamics and optimizing luminosity in high-luminosity colliders.

physics.ins-det↗

arXiv2026

Machine Learning on Heterogeneous, Edge, and Quantum Hardware for Particle Physics (ML-HEQUPP)

The next generation of particle physics experiments will face a new era of challenges in data acquisition, due to unprecedented data rates and volumes along with extreme environments and operational constraints. Harnessing this data for scientific discovery demands real-time inference and decision-making, intelligent data reduction, and efficient processing architectures beyond current capabilities. Crucial to the success of this experimental paradigm are several emerging technologies, such as artificial intelligence and machine learning (AI/ML), silicon microelectronics, and the advent of quantum algorithms and processing. Their intersection includes areas of research such as low-power and low-latency devices for edge computing, heterogeneous accelerator systems, reconfigurable hardware, novel codesign and synthesis strategies, readout for cryogenic or high-radiation environments, and analog computing. This white paper presents a community-driven vision to identify and prioritize research and development opportunities in hardware-based ML systems and corresponding physics applications, contributing towards a successful transition to the new data frontier of fundamental science.

physics.ins-det↗

arXiv2024

Development and Implementation of Advanced Beam Diagnostic and Abort Systems in SuperKEKB

The SuperKEKB/Belle II experiment aims to collect high-statistics data of B meson pairs to explore new physics beyond the Standard Model (SM). SuperKEKB, an upgraded version of the KEKB accelerator, has achieved a world-record luminosity of $4.71 \times 10^{34} \, \mathrm{cm^{-2}s^{-1}}$ in 2022 but continues to strive for higher luminosities. One of the major obstacles is Sudden Beam Loss (SBL) events, which cause substantial beam losses and damage to the Belle~II detector. To find a hint for addressing SBL challenges, advanced beam diagnostic systems and enhanced beam abort systems have been developed. The diagnostic system aims to accurately pinpoint the start of beam losses, while the upgraded abort system quickly disposes of anomalous beams to minimize damage. This paper details the development and implementation of these systems, including high-speed loss monitors, time synchronization with the White Rabbit system, and data acquisition systems. Efforts to understand the mechanisms of SBL events, using acoustic sensors to detect discharges, are also discussed. These measures aim to improve the operational stability and luminosity of SuperKEKB, contributing to the experiment's success.

hep-ex↗

arXiv2023

Social Preferences and Deliberately Stochastic Behavior

This study proposes a tractable stochastic choice model to identify motivations for prosocial behavior, and to explore alternative motivations of deliberate randomization beyond ex-ante fairness concerns. To represent social preferences, we employ an additively perturbed utility model consisting of the sum of expected utility and a nonlinear cost function, where the utility function is purely selfish while the cost function depends on social preferences. Using the cost function, we study stochastic choice patterns to distinguish between stochastic inequity-averse behavior and stochastic shame-mitigating behavior. Moreover, we discuss how our model can complement recent experimental evidence of ex-post and ex-ante fairness concerns.

econ.TH↗

arXiv2019

Search for direct stop pair production with the ATLAS detector

Supersymmetry, which extends the Standard Model (SM) by introducing supersymmetric partners for the SM particles, can provide an elegant solution to the hierarchy problem. One of the most important parameters in supersymmetry is the mass of the supersymmetric partner to the top quark, referred to as stop. In the absence of the stop signature in the previous searches at the LHC, compressed stop searches in which the mass of the stop is close to the mass of the lightest neutralino become more important. In scenarios with compressed mass spectra, the momentum transfer to the decay products of the stop may be small, leading to decay products with transverse momenta of only a few GeV. Hence, the identification and reconstruction of those "soft" objects can play a crucial role in the searches. In this article, recent results from the compressed stop searches in pp collisions at $\sqrt{s}$ =13 TeV with the ATLAS detector and new developments for soft b-hadron tagging techniques are presented.

hep-ex↗

arXiv2017

Search for 3rd generation superpartners with the ATLAS experiment

Two of the most important parameters in supersymmetry are the masses of the stop and sbottom, the supersymmetric partners of the third generation quarks. A stop mass lighter than 1 TeV is favored theoretically; however, "conventional" searches based on the simplified models have not produced experimental evidence for a light stop. It is possible that the light stop evades our searches due to a compressed sparticle mass spectrum. Therefore, the searches are extended to cover a broader range of signal scenarios with different mass splittings between the stop, neutralino(s), and chargino(s). The searches are then interpreted in the context of both simplified models and pMSSM models. Recent ATLAS results from searches for direct stop (sbottom) pair production are presented in final states with jets and missing transverse-momentum (and leptons). The analyses are based on 36 fb$^{-1}$ of $\sqrt{s}$=13 TeV proton-proton collision data recorded with ATLAS detector at the LHC in 2015 and 2016.

hep-ex↗

arXiv2017

Search for supersymmetric partners of third generation quarks in leptonic channels with the ATLAS detector

Two of the most important parameters in supersymmetry are the masses of the stop and sbottom, the supersymmetric partners of the third generation quarks. A stop mass lighter than 1 TeV is favored theoretically, however, conventional searches based on the simplified models have not produced experimental evidence for a light stop. It is possible that the light stop evades our searches due to a compressed sparticle mass spectrum. Therefore, the searches are extended to cover a broader range of signal scenarios with different mass splittings between the stop, neutralino(s), and chargino(s). The searches are then interpreted in the context of both simplified models and pMSSM models. Searches are also performed for various R-parity violating stop (sbottom) models. Recent ATLAS results from searches for direct stop (sbottom) pair production are presented in final states with jets, missing transverse-momentum, and leptons. The analyses are based on 36 fb$^{-1}$ of $\sqrt{s}$=13 TeV proton-proton collision data recorded with ATLAS detector at the LHC in 2015 and 2016.

hep-ex↗