arXiv subjects

Y. Buch

Publications and source records attributed to Y. Buch.

5 recordsLinked to original sources

arXiv2026

Development for the Belle II vertex detector upgrade with depleted monolithic active pixel sensors

The vertex detector upgrade project for the Belle II experiment, based on CMOS depleted monolithic active pixel sensor technology, is planned to be carried out in conjunction with the major modification of the interaction region of the SuperKEKB collider during Long Shutdown 2 from 2032 to 2034. The MAPS sensor, named OBELIX currently under development, is derived from the successor to TJ-Monopix2, with modifications implemented to ensure compatibility with the Belle II trigger system. The new vertex detector consists of two layers of four self-supported consecutive OBELIX sensors, and three layers of discrete OBELIX sensors mounted on mechanical support structures with readout flex circuits attached to the sensors. The detector is arranged cylindrically around the beam pipe at radii ranging from 14 mm to 140 mm. The minimization of the material budget is required in order to enhance physics performance. We present an overview of the project and its latest developments, with particular emphasis on the development of low-material-budget flex circuits employing aluminum conductors.

physics.ins-det↗

arXiv2026

Application of exhaustive simulation flow for advanced performance prediction of monolithic active pixel sensors

Monolithic active pixel sensor (MAPS) developments have pushed the detection performance in various directions, especially relative to timing where nanosecond-level precision is now considered. This evolution calls for a simultaneous upgrade of the simulation tools. We have developed a simulation flow that covers steps from the signal creation in the sensitive volume to the output of the pixel digital logic that performs the time-of-arrival and time-over-threshold (ToA/ToT) measurements. This approach adds several new features to the traditional use the of the TCAD - Allpix Squared duo, among which : the integration of the pixel wells from the layout in order to precisely describe the pixel key characteristics such as leakage and punch-through currents and the coupling of Monte Carlo simulations (Allpix Squared) with high precision electrical simulations (SPICE). The first (Allpix Squared) for the precise description of the current induced at the collection electrode and the second (SPICE) to guarantee high precision simulation of the front-end electronics using realistic signal events. Irradiation is also modeled, both from the charge propagation side (charge trapping) and from the front-end response side (high input signal discharge). We have applied this methodology to the MAPS developed in the context of the Belle II vertex detector upgrade. In this contribution, we detail the key features of the exhaustive simulation flow, present the outcome of the comparison with the TJ-Monopix2 measurements and discuss the interest of the methodology for the development of modern MAPS.

physics.ins-det↗

arXiv2024

The Belle II Detector Upgrades Framework Conceptual Design Report

We describe the planned near-term and potential longer-term upgrades of the Belle II detector at the SuperKEKB electron-positron collider operating at the KEK laboratory in Tsukuba, Japan. These upgrades will allow increasingly sensitive searches for possible new physics beyond the Standard Model in flavor, tau, electroweak and dark sector physics that are both complementary to and competitive with the LHC and other experiments.

hep-ex↗

arXiv2023

Upgrade of Belle II Vertex Detector with CMOS Pixel Technology

The Belle II experiment at KEK in Japan considers upgrading its vertex detector system to address the challenges posed by high background levels caused by the increased luminosity of the SuperKEKB collider. One proposal for upgrading the vertex detector aims to install a 5-layer all monolithic pixel vertex detector based on fully depleted CMOS sensors in 2027. The new system will use the OBELIX MAPS chips to improve background robustness and reduce occupancy levels through small and fast pixels. This causes better track finding, especially for low transverse momenta tracks. This text will focus on the predecessor of the OBELIX sensor, the TJ-Monopix2, presenting laboratory and test beam results on pixel response, efficiency, and spatial resolution.

physics.ins-det↗

arXiv2023

A neural network for beam background decomposition in Belle II at SuperKEKB

We describe a neural network for predicting the background hit rate in the Belle II detector produced by the SuperKEKB electron-positron collider. The neural network, BGNet, learns to predict the individual contributions of different physical background sources, such as beam-gas scattering or continuous top-up injections into the collider, to Belle II sub-detector rates. The samples for learning are archived 1 Hz time series of diagnostic variables from the SuperKEKB collider subsystems and measured hit rates of Belle II used as regression targets. We test the learned model by predicting detector hit rates on archived data from different run periods not used during training. We show that a feature attribution method can help interpret the source of changes in the background level over time.

hep-ex↗