Switchless event building farm for the Belle data acquisition system

We designed a switchless event building farm for the Belle experiment at the KEKB [e.sup.+] [e.sup.-] collider, as a replacement of the existing event builder and the online farm systems. In the new system, PCs are directly interconnected with multiple point-to-point Fast and Gigabit Ethernet connections. The PCs build the detector data in two steps to perform distributed event processing. We set up a test system and confirmed the event building performance meets our new requirements using a realistic prototype software. The system is being installed as sceduled using the summer shutdown time in 2001. Index Terms--Data acquisition, data transfer, event building, event filtering.