Use of an FPGA to identify electromagnetic clusters and isolated hadrons in the ATLAS level-1 calorimeter trigger

Abstract At the full LHC design luminosity of 10 34 cm −2 s −1 , there will be approximately 109 proton–proton interactions per second. The ATLAS level-1 trigger is required to have an acceptance factor of ∼10−3. The calorimeter trigger covers the region |η|⩽5.0, and φ=0 to 2π. The distribution of transverse energy over the trigger phase space is analysed to identify candidates for electrons/photons, isolated hadrons, QCD jets and non-interacting particles. The Cluster Processor of the level-1 calorimeter trigger is designed to identify transverse energy clusters associated with the first two of these. The algorithms based on the trigger tower energies which have been designed to identify s…