000004277 001__ 4277
000004277 005__ 20240509102424.0
000004277 037__ $$aBELLE2-CONF-PROC-2024-010
000004277 041__ $$aeng
000004277 100__ $$aAlice Gabrielli for the SVD collaboration
000004277 245__ $$aThe silicon vertex detector of the Belle II experiment
000004277 260__ $$a$$c2024-04-27
000004277 300__ $$a5
000004277 520__ $$aThe silicon vertex detector (SVD) is a four-layer double-sided strip detector installed at the heart of the Belle II experiment, taking data at the high-luminosity $B$-Factory SuperKEKB since 2019. SVD has been operating smoothly and reliably, showing a stable and above-99\% hit efficiency, and a large signal-to-noise ratio in all sensors.  In June 2022 the data-taking of the Belle II experiment was stopped for the Long Shutdown 1, primarily required to complete the vertex detector (VXD) with the inner two-layer DEPFET detector and to upgrade several components of the accelerator.  This article reports on the excellent performance of SVD in terms of the signal-to-noise ratio, the hit position resolution, as well as the hit-time resolution. We briefly describe the challenges and delicate phases of the VXD re-installation and the SVD status for operation starting in early 2024.  In SVD layer3, which is closest to the interaction point, the average occupancy has been less 0.5\%, well below the estimated limit for acceptable tracking performance. However, higher machine backgrounds are expected at increased luminosity, and so also increased hit occupancy. To enhance the robustness of offline software in a high-background environment, new algorithms of background suppression using the excellent SVD hit-time information have been developed, which allows a significant reduction of the fake rate, while preserving the tracking efficiency. With the increasing luminosity also the radiation levels are expected to increase, with possible deterioration of the sensor performance. The SVD integrated dose is estimated by the correlation of the SVD occupancy with the dose rate measured by the diamonds of the radiation monitor and beam-abort system. The effects of radiation damage are starting and in good agreement with our expectations. So far, no harmful impact due to the radiation damage on the detector performance has been observed. 
000004277 6531_ $$aBelle II 
000004277 6531_ $$aVertex detector 
000004277 6531_ $$aSilicon strip detector
000004277 6531_ $$atracking
000004277 6531_ $$ahigh-luminosity
000004277 8560_ $$falice.gabrielli@pi.infn.it
000004277 8564_ $$uhttps://docs.belle2.org/record/4277/files/BELLE2-CONF-PROC-2024-010.pdf