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SUMMARY:The Silicon Vertex Detector of the Belle II Experiment
DTSTART;VALUE=DATE-TIME:20230905T142000Z
DTEND;VALUE=DATE-TIME:20230905T144000Z
DTSTAMP;VALUE=DATE-TIME:20260410T222829Z
UID:indico-contribution-2978@indico.tlabs.ac.za
DESCRIPTION:Speakers: Abdul Basith Kaliyar ()\nIn June 2022 the data takin
 g of the Belle II experiment was stopped for the Long Shutdown 1 (LS1)\, w
 hich is primarily required to install a new two-layer DEPFET detector (PXD
 ) and upgrade components of the accelerator. The whole silicon tracker (VX
 D) will be extracted from Belle II\, then the outer four-layer double-side
 d strip detector (SVD) is split into its two halves to allow access for th
 e PXD installation. Then a new VXD commissioning phase will begin such tha
 t it will be ready to take data by the end of 2023. We describe the challe
 nges and status of this VXD upgrade. \nIn addition\, we report on the perf
 ormance of the SVD\, which has been operated since 2019. The high hit effi
 ciency and the large signal-to-noise are monitored via online data-quality
  plots. \nThe good cluster-position resolution is estimated using the unbi
 ased residual with respect to the track\, resulting in reasonable agreemen
 t with the expectations. A novel procedure to group SVD hits event-by-even
 t\, based on their time\, has been developed. Using the grouping informati
 on during reconstruction allows to significantly reduce the fake rate whil
 e preserving the tracking efficiency. \nSo far\, in the layer closest to t
 he I.P.\, the SVD average occupancy has been less 0.5%\, which is well bel
 ow the estimated limit for acceptable tracking performance. As the luminos
 ity increases\, higher machine backgrounds are expected and the excellent 
 hit-time information in SVD can be exploited for background rejection. We 
 have developed a method that uses the SVD hit-time to estimate the collisi
 on time (event-T0) with similar precision to the estimate based on the dri
 ft chamber. The execution time needed to compute SVD event-T0 is three ord
 ers of magnitude smaller\, allowing a faster online reconstruction that is
  crucial in a high luminosity regime. Furthermore\, the front-end chip (AP
 V25) is operated in “multi-peak” mode\, which reads six samples. To re
 duce background occupancy\, trigger dead-time and data size\, a 3/6-mixed 
 acquisition mode\, based on the timing precision of the trigger\, has been
  successfully tested in physics runs.\nFinally\, concerning the radiation 
 damage\, the SVD dose is estimated by the correlation of the SVD occupancy
  with the dose measured by the diamonds of the monitoring and beam-abort s
 ystem. Although the sensor current and the strip noise have shown a modera
 te increase due to radiation\, we expect the detector performance will not
  be seriously degraded during the lifespan of the detector.\n\nhttps://ind
 ico.tlabs.ac.za/event/112/contributions/2978/
LOCATION: Meeting Room 2.64 - 2.66
URL:https://indico.tlabs.ac.za/event/112/contributions/2978/
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