Speaker
Description
Run 2 of the Belle II experiment began in 2024. With new data, the SVD confirmed high hit efficiency, large signal-to-noise and good cluster-position resolution. SuperKEKB’s instantaneous luminosity is expected to increase significantly, resulting in a larger SVD occupancy caused by beam-related background. Considerable efforts have been made to improve the SVD-reconstruction software by exploiting the excellent SVD hit-time resolution to determine the collision time and reject out-of-time hits caused by the beam-related background. A novel procedure to group SVD hits event-by-event, based on their time, has been developed by using the grouping information during reconstruction, significantly reducing the fake rate, while preserving the tracking efficiency. The front-end chip (APV25) is operated in “multi-peak” mode, reading six samples. During data taking, we tested a 3/6-mixed acquisition mode, based on the timing precision of the trigger, that reduced background occupancy, trigger dead-time and data size. Studies show a moderate radiation-induced increase in sensor current and strip noise. However, such damage will not degrade the performance during the lifespan of the detector.
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