A next generation B-factory experiment, Belle II, is now being constructed at KEK in Japan. The upgraded accelerator SuperKEKB is designed to have the maximum luminosity of 8×10 35 cm −2 s −1 that is a factor 40 higher than the current world record. As a consequence, the Belle II detector yields a data stream of the event size ∼1 MB at a Level 1 rate of 30 kHz. The Belle II High Level Trigger (HLT) is designed to reduce the Level 1 rate to 1/5 by performing the real time full event

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... n and by applying the physics level event selection as the software trigger. In this paper, the development of the high level trigger system for Belle II and its performance is discussed.