PoS - Proceedings of Science
Volume 398 - The European Physical Society Conference on High Energy Physics (EPS-HEP2021) - T12: Detector R&D and Data Handling
The operation and performance of the TOP detector at the Belle II experiment
K. Kojima*  on behalf of the Belle II TOP group
Full text: pdf
Pre-published on: March 01, 2022
Published on: May 12, 2022
The SuperKEKB/Belle II experiment, the successor of the KEKB/Belle experiment at KEK, started the physics data taking with the full detector system in March 2019. The Time-of-Propagation (TOP) detector was integrated into the Belle II detector for charged particle identification in the barrel region. The TOP detector mainly consists of quartz radiators, Micro-Channel-Plate (MCP) PMTs, and front-end electronics. It reconstructs a ring image of Cherenkov photons generated by an incident particle. It measures the timing of each detected photon with an accuracy of less than $100~\mathrm{ps}$ for good $K/\pi$ separation.

In the operation of the TOP detector, harsh beam-induced background in the high luminosity environment is one of the critical issues to keep the particle identification performance. We developed various tools to monitor MCP-PMT performance and to identify and fix errors arising from front-end electronics during data taking. The TOP detector provides $85\%$ $K$ identification efficiency at a $10\%$ $\pi$ misidentification rate in the data at the early stage of the experiment. In these proceedings, we present the operation status and the performance by the summer of 2021.
DOI: https://doi.org/10.22323/1.398.0803
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