Vertexing and Tracking SW at Belle II

Abstract

Belle II is a B factory experiment aiming to start physics data taking in 2017. It is currently being set up at the SuperKEKB accelerator at the KEK facility in Tsukuba (Japan), an asymmetric e + e − collider which aims to achieve an unprecedented instantaneous luminosity of 8 • 10 35 Hz/cm 2. This forty-fold increase over predecessor experiments is achieved by employing a novel nanobeam scheme. Originally developed for the now-defunct SuperB experiment, this scheme allows a significant increase in luminosity at only modest increases of beam currents. Challenges for the vertex detector result from increased data and background rates. At full luminosity, physics data will be recorded at a rate of 30 kHz. The radiation-hard DEPFET-sensors of the innermost layer of the vertex detector will be read out employing a novel data-reduction scheme using selective detector read out based on online reconstruction of event data. Belle II uses a software framework in which data handling is unified between various data processing modules. In this way, tasks can be divided flexibly and the same software framework can be used for a diversity of tasks ranging from the high-level trigger to final processing of plots for publications. Tracking and vertexing modules are currently under development and we will discuss their features.

The track finding algorithm of the Belle II vertex detectors

“…The implementation of the track finding algorithm for the Belle II vertex detectors is implemented in C++ 11 and is part of the Belle II analysis software framework [6].…”

The beam test measurements of the Belle II vertex detector modules

“…That is, reconstructed hits are fitted, tracks are extrapolated to PXD and ROIs are defined. In the express reconstruction, the tracking is repeated with both SVD and PXD hits contained in ROIs [10]. In offline re-processing, both PXD and SVD data are available and in the following, for clarity, the processing chain is described as done offline.…”

Performance studies of the Belle II Silicon Vertex Detector with data taken at the DESY test beam in April 2016

“…The track finding is performed by the track finding software implemented in the Belle II software framework [7]. The alignment of the sensors is done by the Belle II alignment framework utilizing the Millipede package.…”