Level-2 calorimeter trigger upgrade at CDF

The CDF Run II [1] Level 2 calorimeter trigger is implemented in hardware and is based on a simple algorithm that was used in Run I. This system has worked well for Run II at low luminosity. As the Tevatron instantaneous luminosity increases, the limitation due to this simple algorithm starts to become clear. As a result, some of the most important jet and MET (Missing ET) related triggers have large growth terms in cross section at higher luminosity. In this paper, we present an upgrade of the L2CAL system which makes the full calorimeter trigger tower information directly available to the Level 2 decision CPU. This upgrade is based on the Pulsar [2], a general purpose VME board developed at CDF and already used for upgrading both the Level 2 global decision crate [3] and the Level 2 Silicon Vertex Tracking [4]. The upgrade system allows more sophisticated algorithms to be implemented in software and both Level 2 jets and MET can be made nearly equivalent to offline quality, thus significantly improving the performance and flexibility of the jet and MET related triggers. This is a natural expansion of the already-upgraded Level 2 trigger system, and is a big step forward to improve the CDF triggering capability at Level 2. This paper describes the design, the hardware and software implementation and the performance of the upgrade system. Index Terms--Calorimeter, CDF, FPGA, HEP, trigger.