Operational experience of the Belle II pixel detector

Belle-II DEPFET and PXD Collaboration: et al.
The Belle II experiment at the SuperKEKB accelerator has started its physics data taking with the full detector setup in March 2019. It aims to collect 40 times more e+ e- collision data compared with its predecessor Belle experiment. The Belle II pixel detector (PXD) is based on the Depleted P-channel Field Effect Transistor (DEPFET) technology. The PXD plays an important role in the tracking and vertexing of the Belle II detector. Its two layers are arranged at radii of 14 mm and 22 mm around the interaction point. The sensors are thinned down to 75 m to minimize multiple scattering, and each module has interconnects and ASICs integrated on the sensor with silicon frames for mechanical support. PXD showed good performance during data taking. It also faces several operational challenges due to the high background level from the SuperKEKB accelerator, such as the damage from beam loss events, the drift in the HV working point due to radiation effect, and the impact of the high background.
This work is supported by MEXT, WPI, and JSPS (Japan); MSMT, GAUK 404316 (Czech Republic), MSCA-RISE project JENNIFER-2 (EU grant 822070); Federal Ministry of Education and Research (BMBF, Germany); CIDEGENT/2018/020 of Generalitat Valenciana (Spain); National Natural Science Foundation of China (No. 11435013); and research grants S-1440-0321, S-0256-1438, and S-0280-1439 (University of Tabuk, KSA, Saudi Arabia ).