Ping Ni

2022
University of Tokyo, Department of Physics, Graduate School of Science Tokyo

Abstract: The Belle II experiment hosted by KEK has started taking physics data since 2019, committed to finding new physics beyond the Standard Model. The SuperKEKB has been upgraded to collide e− and e+ beams with a designed luminosity of 6×1035 cm−2s−1 which is 30 times higher than the predecessor, the Belle experiment. Accompanied by the higher luminosity is the higher beam-originated background, making it challenging to operate the Level-1 trigger system while keeping high efficiency for physics events and trigger rate smaller than the limit of 30 kHz. We evaluate the performance of the 2D track trigger at the designed luminosity with Monte Carlo simulation and clarify that the trigger rate is expected to exceed the limit of 30 kHz due to fake tracks. An upgraded 2-dimensional tracking algorithm named “Full-hit algorithm” has been developed in order to resolve this issue. The algorithm is designed as a simulation software and succeeded in reducing the trigger rate from the fake tracks below 1 kHz. The algorithm is optimized as a digital circuit on the Field Programmable Gate Array and successfully implemented in a new generation of the Belle II universal trigger board. The Full-hit is under commissioning and is planned to be used for physics operation in 2023 after the long shutdown of the Belle II.

Note: Presented on 09 08 2022
Note: MSc