The Silicon Vertex Detector of the Belle II Experiment

The Belle II experiment started taking data at the SuperKEKB collider in spring 2019. As part of the inner tracker system, the silicon vertex detector (SVD) has been operating reliably. It provided good data quality, a good signal-to-noise ratio, an excellent hit efficiency greater than 99% and precise spatial resolution, which result in good tracking efficiency. The current occupancy, which is dominated by beam-background hits, is around 0.5% in the innermost layer and does so far not cause problems to the SVD data reconstruction. Due to the estimated increase in occupancy at higher luminosity in the next years, specific strategies aiming to preserve the tracking performance were developed and tested on data. Strip noise, sensor currents and depletion voltages have been measured to check for the first effects of radiation damage. So far no harmful impact on the detector performance has been observed. Extrapolations for the next years do not imply upcoming problems, although these background estimates are still affected by large uncertainties. No damage due to beam losses or sudden intense radiation bursts were detected.