The Belle II Silicon Vertex Detector

Abstract

The KEKB machine and the Belle experiment in Tsukuba (Japan) are now undergoing an upgrade, leading to an ultimate luminosity of 8 × 10 35 cm −2 s −1 in order to measure rare decays in the B system with high statistics. The previous vertex detector cannot cope with this 40-fold increase of luminosity and thus needs to be replaced. Belle II will be equipped with a two-layer Pixel Detector surrounding the beam pipe, and four layers of double-sided silicon strip sensors at higher radii than the old detector. The Silicon Vertex Detector (SVD) will have a total sensitive area of 1.13 m 2 and 223,744 channelstwice as many as its predecessor.All silicon sensors will be made from 150 mm wafers in order to maximize their size and thus to reduce the relative contribution of the support structure. The forward part has slanted sensors of trapezoidal shape to improve the measurement precision and to minimize the amount of material as seen by particles from the vertex. Fast-shaping front-end amplifiers will be used in conjunction with an online hit time reconstruction algorithm in order to reduce the occupancy to the level of a few percent at most. A novel "Origami" chip-on-sensor scheme is used to minimize both the distance between strips and amplifier (thus reducing the electronic noise) as well as the overall material budget.This report gives an overview on the status of the Belle II SVD and its components, including sensors, front-end detector ladders, mechanics, cooling and the readout electronics.

FPGA based data read-out system of the Belle 2 pixel detector

“…The goal of the campaign was to test the integration of the data-acquisition and online-data-reduction systems of the Belle 2 vertex detector. The test was performed on a detector prototype consisting of one layer of the pixel detector and four layers of the double-sided silicon strip detector [10]. While the detector provides enough planes for track reconstruction, the AIDA telescope was used to estimate the performance of the detector.…”

Ultra-transparent DEPFET pixel detectors for future electron-positron experiments

“…It consists of a DEPFET sensor with 480×192 pixels, with a 50×75 µm 2 pixel pitch, resulting in an active area of 39.0×9.6 mm 2 . The goal of the test beam period was the combined operation of a small sector of final-design components of the Belle II vertex detector; namely, a thin close-to-final size DEPFET sensor and 4 silicon micro-strip modules [16], arranged in a configuration that mimics the final Belle II vertex detector geometry. The readout of such detector system was performed using a scaled version of the final full DAQ chain [17] [18] [19].…”

Machine learning: hit time finding with a neural network

“…At the High Energy Accelerator Research Organization (KEK) in Tsukuba, Japan, the Belle II experiment [1] will explore the asymmetry between matter and antimatter and search for new physics beyond the standard model. One of its inner tracking systems is the Silicon Vertex Detector (figure 1) [2], which consists of 172 orthogonal double-sided strip sensors. They are arranged cylindrically in four layers around the Pixel Detector to measure the tracks of the collision products of electrons and positrons.…”