The Level-3 Trigger at the CDF Experiment at Tevatron Run II

We describe the filtering and analysis software running in the Collider Detector at Fermilab (CDF) Run II Level-3 trigger, as well as the client- and event-driven data hub system. These systems constitute critical components of the data acquisition system of the CDF detector. The Level-3 trigger is responsible for reconstructing the events and forming the final trigger decision. The consumer-server/logger (CSL) system receives the accepted physics events from multiple connections and writes them to disk in multiple streams, while distributing them to online analysis programs (consumers). Since 2001, the system has been running successfully at high throughput rates: the Level-3 trigger reduces the event rate from 350 Hz to about 100 Hz with an average event size of 150 kB, while the CSL is able to process up to 22 MB/s of constant event logging. We describe these systems in detail and report on their current performance. We briefly outline upgrade plans for the remainder of Tevatron Run II.