부산대학교 도서관

The Belle II experiment started to take data of electron–positron collisions provided by the SuperKEKB accelerator, with all subdetectors from March 2019. The collected data are selected by a software-based high-level trigger (HLT) system and stored on online storage. After storing the data, the online storage sends the data to an express-reconstruction system for semireal-time data quality monitoring (DQM) and event display. The HLT system is built on the ZeroMQ networking library, but the online storage and express-reconstruction system are built on the ring buffer and transmission control protocol/internet protocol (TCP/IP) socket-based framework. To improve stability and future maintainability, we develop a new online storage and express-reconstruction system using the ZeroMQ library. The new systems have a few additional improvements. First, the online storage supports the ROOT output file format with compression. This reduces the online file size, necessary network bandwidth for the online-to-offline file transfer, and offline computing resource usage. Second, two types of express-reconstruction systems are prepared based on the HLT results: for randomly sampled data and for physics-flagged data by the HLT system. The separate express-reconstruction system can process a larger number of statistics of physics-flagged events.